[Xiaomi Mi Pad 4 Plus ROMs, Kernels, Recoveries, & ] idcom:
Dirty installed and it booted fine. Have tracked down that the sdcard will mount if vfat formatted but not exfat formatted. When you format in the system it happily formats the card to exfat which it then can't mount.

When I put it on my Linux PC it recognises exfatmand can mount but not on the tablet.

Below is output of proc/filesystem and mount with vfat card in.

~$ cat /proc/filesystems

nodev sysfs

nodev rootfs

nodev ramfs

nodev bdev

nodev proc

nodev cpuset

nodev cgroup

nodev cgroup2

nodev tmpfs

nodev configfs

nodev debugfs

nodev tracefs

nodev sockfs

nodev pipefs

nodev devpts

ext3

ext2

ext4

vfat

sdfat

exfat

nodev ecryptfs

nodev sdcardfs

fuseblk

nodev fuse

nodev fusectl

f2fs

nodev pstore

nodev selinuxfs

nodev functionfs

~$ mount

/dev/block/mmcblk0p13 on / type ext4 (ro,seclabel,nodev,relatime,discard)

tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,size=1893556k,nr_inodes=473389,mode=755)

devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600)

none on /dev/cg2_bpf type cgroup2 (rw,nosuid,nodev,noexec,relatime)

none on /dev/cpuctl type cgroup (rw,nosuid,nodev,noexec,relatime,cpu)

none on /dev/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset,noprefix,release_agent=/sbin/cpuset_release_agent)

none on /dev/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)

none on /dev/memcg type cgroup (rw,nosuid,nodev,noexec,relatime,memory)

none on /dev/stune type cgroup (rw,nosuid,nodev,noexec,relatime,schedtune)

adb on /dev/usb-ffs/adb type functionfs (rw,relatime)

proc on /proc type proc (rw,relatime,gid=3009,hidepid=2)

sysfs on /sys type sysfs (rw,seclabel,relatime)

selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)

tracefs on /sys/kernel/tracing type tracefs (rw,seclabel,relatime)

debugfs on /sys/kernel/debug type debugfs (rw,seclabel,relatime)

tracefs on /sys/kernel/debug/tracing type tracefs (rw,seclabel,relatime)

none on /sys/fs/fuse/connections type fusectl (rw,relatime)

pstore on /sys/fs/pstore type pstore (rw,seclabel,nosuid,nodev,noexec,relatime)

tmpfs on /mnt type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1893556k,nr_inodes=473389,mode=755,gid=1000)

tmpfs on /mnt/installer type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1893556k,nr_inodes=473389,mode=755,gid=1000)

/dev/fuse on /mnt/installer/0/emulated type fuse (rw,lazytime,nosuid,nodev,noexec,noatime,user_id=0,group_id=0,allow_other)

/data/media on /mnt/installer/0/emulated/0/Android/data type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal,unshared_obb)

/data/media on /mnt/installer/0/emulated/0/Android/obb type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7,derive_gid,default_normal,unshared_obb)

/dev/fuse on /mnt/installer/0/B26B-8036 type fuse (rw,lazytime,nosuid,nodev,noexec,noatime,user_id=0,group_id=0,allow_other)

tmpfs on /mnt/androidwritable type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1893556k,nr_inodes=473389,mode=755,gid=1000)

/dev/fuse on /mnt/androidwritable/0/emulated type fuse (rw,lazytime,nosuid,nodev,noexec,noatime,user_id=0,group_id=0,allow_other)

/data/media on /mnt/androidwritable/0/emulated/0/Android/data type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal,unshared_obb)

/data/media on /mnt/androidwritable/0/emulated/0/Android/obb type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal,unshared_obb)

/dev/fuse on /mnt/androidwritable/0/B26B-8036 type fuse (rw,lazytime,nosuid,nodev,noexec,noatime,user_id=0,group_id=0,allow_other)

/dev/block/mmcblk0p48 on /mnt/vendor/persist type ext4 (rw,seclabel,nosuid,nodev,noatime,data=ordered)

/data/media on /mnt/runtime/default/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal,unshared_obb)

/data/media on /mnt/runtime/read/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=23,derive_gid,default_normal,unshared_obb)

/data/media on /mnt/runtime/write/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7,derive_gid,default_normal,unshared_obb)

/data/media on /mnt/runtime/full/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7,derive_gid,default_normal,unshared_obb)

/dev/fuse on /mnt/user/0/emulated type fuse (rw,lazytime,nosuid,nodev,noexec,noatime,user_id=0,group_id=0,allow_other)

/data/media on /mnt/user/0/emulated/0/Android/data type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal,unshared_obb)

/data/media on /mnt/user/0/emulated/0/Android/obb type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal,unshared_obb)

/data/media on /mnt/pass_through/0/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7,derive_gid,default_normal,unshared_obb)

/dev/block/vold/public:179,65 on /mnt/media_rw/B26B-8036 type vfat (rw,dirsync,nosuid,nodev,noexec,noatime,gid=1023,fmask=0007,dmask=0007,allow_utime=0020,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro)

/mnt/media_rw/B26B-8036 on /mnt/runtime/default/B26B-8036 type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,mask=6)

/mnt/media_rw/B26B-8036 on /mnt/runtime/read/B26B-8036 type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,mask=18)

/mnt/media_rw/B26B-8036 on /mnt/runtime/write/B26B-8036 type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,mask=18)

/mnt/media_rw/B26B-8036 on /mnt/runtime/full/B26B-8036 type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,mask=7)

/dev/fuse on /mnt/user/0/B26B-8036 type fuse (rw,lazytime,nosuid,nodev,noexec,noatime,user_id=0,group_id=0,allow_other)

/mnt/media_rw/B26B-8036 on /mnt/pass_through/0/B26B-8036 type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,mask=7)

/dev/block/mmcblk0p14 on /vendor type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p25 on /vendor/firmware_mnt type vfat (ro,context=u:object_r:firmware_file:s0,relatime,uid=1000,gid=1000,fmask=0337,dmask=0227,codepage=437,iocharset=iso8859-1,shortname=lower,errors=remount-ro)

/dev/block/mmcblk0p42 on /vendor/bt_firmware type vfat (ro,context=u:object_r:bt_firmware_file:s0,relatime,uid=1002,gid=3002,fmask=0337,dmask=0227,codepage=437,iocharset=iso8859-1,shortname=lower,errors=remount-ro)

/dev/block/mmcblk0p27 on /vendor/dsp type ext4 (ro,seclabel,nosuid,nodev,relatime,data=ordered)

tmpfs on /apex type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1893556k,nr_inodes=473389,mode=755)

/dev/block/mmcblk0p13 on /apex/com.android.mediaprovider type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.conscrypt type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.tethering type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.art type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.permission type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.adbd type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.ipsec type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.media type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.wifi type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.extservices type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.os.statsd type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.cellbroadcast type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.sdkext type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.runtime type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.media.swcodec type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.neuralnetworks type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.i18n type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.resolv type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p13 on /apex/com.android.tzdata type ext4 (ro,seclabel,relatime,discard)

/dev/block/mmcblk0p14 on /apex/com.android.vndk.v30 type ext4 (ro,seclabel,relatime,discard)

tmpfs on /linkerconfig type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1893556k,nr_inodes=473389,mode=755)

tmpfs on /linkerconfig type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1893556k,nr_inodes=473389,mode=755)

none on /acct type cgroup (rw,nosuid,nodev,noexec,relatime,cpuacct)

none on /config type configfs (rw,nosuid,nodev,noexec,relatime)

/dev/block/mmcblk0p64 on /data type ext4 (rw,lazytime,seclabel,nosuid,nodev,noatime,discard,noauto_da_alloc,resgid=1065,data=ordered)

/dev/block/mmcblk0p64 on /data/user/0 type ext4 (rw,lazytime,seclabel,nosuid,nodev,noatime,discard,noauto_da_alloc,resgid=1065,data=ordered)

/dev/block/mmcblk0p49 on /cache type ext4 (rw,seclabel,nosuid,nodev,noatime,data=ordered)

tmpfs on /data_mirror type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1893556k,nr_inodes=473389,mode=700,gid=1000)

/dev/block/mmcblk0p64 on /data_mirror/data_ce/null type ext4 (rw,lazytime,seclabel,nosuid,nodev,noatime,discard,noauto_da_alloc,resgid=1065,data=ordered)

/dev/block/mmcblk0p64 on /data_mirror/data_ce/null/0 type ext4 (rw,lazytime,seclabel,nosuid,nodev,noatime,discard,noauto_da_alloc,resgid=1065,data=ordered)

/dev/block/mmcblk0p64 on /data_mirror/data_de/null type ext4 (rw,lazytime,seclabel,nosuid,nodev,noatime,discard,noauto_da_alloc,resgid=1065,data=ordered)

/dev/block/mmcblk0p64 on /data_mirror/cur_profiles type ext4 (rw,lazytime,seclabel,nosuid,nodev,noatime,discard,noauto_da_alloc,resgid=1065,data=ordered)

tmpfs on /storage type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1893556k,nr_inodes=473389,mode=755,gid=1000)/dev/fuse on /storage/emulated type fuse (rw,lazytime,nosuid,nodev,noexec,noatime,user_id=0,group_id=0,allow_other)

/data/media on /storage/emulated/0/Android/data type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal,unshared_obb)

/data/media on /storage/emulated/0/Android/obb type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal,unshared_obb)

/dev/fuse on /storage/B26B-8036 type fuse (rw,lazytime,nosuid,nodev,noexec,noatime,user_id=0,group_id=0,allow_other)

~$