[Android Q&A, Help & Troubleshooting] dazz.:
Greetings everyone. I'm trying to figure out the size of my userdata partition in my new Cubot Nova running Android 8.1 Oreo.

On older devices I managed to do this by running the following commands:

adb shell ls -al /dev/block/platform/bootdevice/by-name --------------> To list my partitions by name and find the actual userdata partition name. In my case, it's /dev/block/mmcblk0p33

Z:\Android\devices\Cubot Nova\adb platform-tools>adb shell ls -al /dev/block/platform/bootdevice/by-name
total 0
drwxr-xr-x 2 root root 780 2019-11-28 19:47 .
drwxr-xr-x 4 root root 860 2019-11-28 19:47 ..
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 boot -> /dev/block/mmcblk0p25
lrwxrwxrwx 1 root root 20 2019-11-28 19:47 boot_para -> /dev/block/mmcblk0p1
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 cache -> /dev/block/mmcblk0p32
lrwxrwxrwx 1 root root 20 2019-11-28 19:47 expdb -> /dev/block/mmcblk0p4
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 flashinfo -> /dev/block/mmcblk0p35
lrwxrwxrwx 1 root root 20 2019-11-28 19:47 frp -> /dev/block/mmcblk0p5
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 gz1 -> /dev/block/mmcblk0p18
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 gz2 -> /dev/block/mmcblk0p19
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 lk -> /dev/block/mmcblk0p21
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 lk2 -> /dev/block/mmcblk0p22
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 loader_ext1 -> /dev/block/mmcblk0p23
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 loader_ext2 -> /dev/block/mmcblk0p24
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 logo -> /dev/block/mmcblk0p26
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 mcupmfw -> /dev/block/mmcblk0p17
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 md1dsp -> /dev/block/mmcblk0p15
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 md1img -> /dev/block/mmcblk0p14
lrwxrwxrwx 1 root root 20 2019-11-28 19:47 metadata -> /dev/block/mmcblk0p8
lrwxrwxrwx 1 root root 20 2019-11-28 19:47 nvcfg -> /dev/block/mmcblk0p6
lrwxrwxrwx 1 root root 20 2019-11-28 19:47 nvdata -> /dev/block/mmcblk0p7
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 nvram -> /dev/block/mmcblk0p20
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 odmdtbo -> /dev/block/mmcblk0p27
lrwxrwxrwx 1 root root 20 2019-11-28 19:47 para -> /dev/block/mmcblk0p3
lrwxrwxrwx 1 root root 23 2019-11-28 19:47 preloader_a -> /dev/block/mmcblk0boot0
lrwxrwxrwx 1 root root 23 2019-11-28 19:47 preloader_b -> /dev/block/mmcblk0boot1
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 proinfo -> /dev/block/mmcblk0p13
lrwxrwxrwx 1 root root 20 2019-11-28 19:47 protect1 -> /dev/block/mmcblk0p9
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 protect2 -> /dev/block/mmcblk0p10
lrwxrwxrwx 1 root root 20 2019-11-28 19:47 recovery -> /dev/block/mmcblk0p2
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 sdrpmb -> /dev/block/mmcblk0p34
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 sec1 -> /dev/block/mmcblk0p12
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 seccfg -> /dev/block/mmcblk0p11
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 spmfw -> /dev/block/mmcblk0p16
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 system -> /dev/block/mmcblk0p31
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 tee1 -> /dev/block/mmcblk0p28
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 tee2 -> /dev/block/mmcblk0p29
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 userdata -> /dev/block/mmcblk0p33
lrwxrwxrwx 1 root root 21 2019-11-28 19:47 vendor -> /dev/block/mmcblk0p30

Then I would run tune2fs -l /dev/block/mmcblk0p33 in the shell to get the partition info (block count and block size) to calculate, but it's not working. I get the following error message:

tune2fs 1.43.3 (04-Sep-2016)
tune2fs: Bad magic number in super-block while trying to open /dev/block/mmcblk0p33

I googled the error message, but I couldn't find anything specific to Android, just Linux. Can someone please help me figure out what I'm doing wrong?.

Is there's another way to get the partition size?

I need it to perform backups with SP Flash Tools. TWRP is unable to decrypt my phone or mount it's internal storage, so that's not an option

Thanks in advance

EDIT: I should have mentioned that the phone is rooted via Magisk, and I run the tune2fs command with superuser access.