[Sony Cross-Device General] serajr:
Bro, as you know I don't own device yet (but bought - XA2 Ultra).

This are partitions infos from an XA2 user, running some shell commands:

H3123:/ # cat /proc/mounts
rootfs / rootfs ro,seclabel 0 0
sysfs /sys sysfs rw,seclabel,relatime 0 0
/dev/block/mmcblk0p79 /system_root ext4 ro,seclabel,relatime,data=ordered 0 0
/dev/block/mmcblk0p79 /system ext4 ro,seclabel,relatime,data=ordered 0 0
tmpfs /dev tmpfs rw,seclabel,nosuid,relatime,size=1385792k,nr_inodes=346448,mode=755 0 0
devpts /dev/pts devpts rw,seclabel,relatime,mode=600 0 0
proc /proc proc rw,relatime,gid=3009,hidepid=2 0 0
selinuxfs /sys/fs/selinux selinuxfs rw,relatime 0 0
/dev/block/platform/soc/c0c4000.sdhci/by-name/vendor_b /vendor ext4 ro,seclabel,relatime,discard,data=ordered 0 0
debugfs /sys/kernel/debug debugfs rw,seclabel,relatime 0 0
none /acct cgroup rw,relatime,cpuacct 0 0
none /dev/stune cgroup rw,relatime,schedtune 0 0
tmpfs /mnt tmpfs rw,seclabel,relatime,size=1385792k,nr_inodes=346448,mode=755,gid=1000 0 0
none /config configfs rw,relatime 0 0
none /dev/memcg cgroup rw,relatime,memory 0 0
none /dev/cpuctl cgroup rw,relatime,cpu 0 0
none /dev/cpuset cgroup rw,relatime,cpuset,noprefix,release_agent=/sbin/cpuset_release_agent 0 0
pstore /sys/fs/pstore pstore rw,seclabel,relatime 0 0
/dev/block/bootdevice/by-name/userdata /data ext4 rw,seclabel,nosuid,nodev,noatime,discard,noauto_da_alloc,data=ordered 0 0
/dev/block/bootdevice/by-name/modem_b /firmware 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 0 0
/dev/block/bootdevice/by-name/bluetooth_b /bt_firmware 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 0 0
/dev/block/bootdevice/by-name/dsp_b /dsp ext4 ro,seclabel,nosuid,nodev,relatime,data=ordered 0 0
/dev/block/bootdevice/by-name/oem_b /oem ext4 ro,seclabel,relatime,data=ordered 0 0
/dev/block/bootdevice/by-name/persist /persist ext4 rw,seclabel,nosuid,nodev,noatime,data=ordered 0 0
/dev/block/bootdevice/by-name/LTALabel /lta-label ext4 ro,context=u:object_r:lta_label:s0,nosuid,nodev,noexec,noatime,data=ordered 0 0
/dev/block/bootdevice/by-name/appslog /rca ext4 rw,seclabel,nosuid,nodev,noexec,noatime,discard,data=ordered 0 0
/dev/block/bootdevice/by-name/diag /idd ext4 rw,seclabel,nosuid,nodev,noexec,noatime,discard,data=ordered 0 0
tmpfs /storage tmpfs rw,seclabel,relatime,size=1385792k,nr_inodes=346448,mode=755,gid=1000 0 0
tracefs /sys/kernel/debug/tracing tracefs rw,seclabel,relatime 0 0
tmpfs /sbin tmpfs rw,seclabel,relatime,size=1385792k,nr_inodes=346448 0 0
/dev/block/mmcblk0p79 /sbin/.core/mirror/system ext4 ro,seclabel,relatime,data=ordered 0 0
/dev/block/platform/soc/c0c4000.sdhci/by-name/vendor_b /sbin/.core/mirror/vendor ext4 ro,seclabel,relatime,discard,data=ordered 0 0
/dev/block/bootdevice/by-name/userdata /sbin/.core/mirror/bin ext4 rw,seclabel,nosuid,nodev,noatime,discard,noauto_da_alloc,data=ordered 0 0
/dev/block/loop0 /sbin/.core/img ext4 rw,seclabel,relatime,data=ordered 0 0
/dev/block/bootdevice/by-name/Qnovo /mnt/qns ext4 rw,seclabel,nosuid,nodev,noexec,noatime,discard,data=ordered 0 0
adb /dev/usb-ffs/adb functionfs rw,relatime 0 0
/data/media /mnt/runtime/default/emulated sdcardfs rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6 0 0
/data/media /storage/emulated sdcardfs rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6 0 0
/data/media /mnt/runtime/read/emulated sdcardfs rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=23 0 0
/data/media /mnt/runtime/write/emulated sdcardfs rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7 0 0
/dev/block/vold/public:179,65 /mnt/media_rw/2817-157C texfat rw,dirsync,nosuid,nodev,noexec,relatime,uid=1023,gid=1023,umask=0007,allow_utime=0020,codepage=437,utf8,min_prealloc_size=64k,max_prealloc_size=121910k,writeback_boundary=4M,readahead=2M,fail_safe,hidden=show,errors=continue 0 0
/mnt/media_rw/2817-157C /mnt/runtime/default/2817-157C sdcardfs rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,mask=6 0 0
/mnt/media_rw/2817-157C /storage/2817-157C sdcardfs rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,mask=6 0 0
/mnt/media_rw/2817-157C /mnt/runtime/read/2817-157C sdcardfs rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,mask=18 0 0
/mnt/media_rw/2817-157C /mnt/runtime/write/2817-157C sdcardfs rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,mask=18 0 0
/dev/block/bootdevice/by-name/userdata /sbin/.core/db-0/magisk.db ext4 rw,seclabel,nosuid,nodev,noatime,discard,noauto_da_alloc,data=ordered 0 0

H3123:/ # ls /dev/block/bootdevice/by-name
LTALabel abl_b bluetooth_b cmnlib64_a ddr diag dsp_b fsmetadata keymaster_b mdtp_a misc modemst2 persist rdimage_a sec storsec tz_a tzxflattest_a vendor_b xfl_b
Qnovo apdp boot_a cmnlib64_b devcfg_a dip frp hyp_a keystore mdtp_b modem_a msadp pmic_a rdimage_b splash system_a tz_b tzxflattest_b xbl_a xflkeystore
TA appslog boot_b cmnlib_a devcfg_b dpo fsc hyp_b limits mdtpsecapp_a modem_b oem_a pmic_b rpm_a ssd system_b tzxfl_a userdata xbl_b xflkeystorebak
abl_a bluetooth_a cdt cmnlib_b devinfo dsp_a fsg keymaster_a logfs mdtpsecapp_b modemst1 oem_b rddata rpm_b sti toolsfv tzxfl_b vendor_a xfl_a

As you can see, _a and _b are present on almost all partitions.

Hope that helps you somehow for now!