[SOLVED] Ubuntu disk space usage after upgrade from 20.04 to 22.04

Hello, everyone. Recently I finally decided to update my system, and right after the update ran into a problem: before update baobab showed ~22 GB avaliable space, and after the update it went down to around 8.

Here's some info, that might be relevant:

df output:

Filesystem     1K-blocks     Used Available Use% Mounted on
tmpfs             788700     1976    786724   1% /run
/dev/nvme0n1p8  53050368 48246568   4054792  93% /
tmpfs            3943496        0   3943496   0% /dev/shm
tmpfs               5120        4      5116   1% /run/lock
/dev/nvme0n1p8  53050368 48246568   4054792  93% /home
/dev/nvme0n1p7    998060   133944    795304  15% /boot
/dev/nvme0n1p1    364544    89768    274776  25% /boot/efi
tmpfs             788696      104    788592   1% /run/user/1000

du -h / shows 23G, du -h /home — 13G. Overall I have 54.3G disk space, so (23+13)/54 doesn't add up to 93%

sudo lsof | grep deleted | wc -l shows 8433 deleted files that are still in use.

I also tried booting with liveUSB and running 'check' on partition via GParted.

I did some research online:

• https://forum.manjaro.org/t/baobab-shows-14gb-less-usage-where-is-the-rest/109527 - seems like a similar problem, but does not address huge du/df difference, also doesn't provide solution for me
• https://unix.stackexchange.com/questions/414417/du-not-accounting-for-space-shown-by-df helped me understend difference between du/dh, so I provided output of lsof as suggested.
• a lot of other stackoverflow posts, all having similar answers, that didn't help me

I tried some methods to locate what consumes all the space, but couldn't figure it out. Also, the problem seems to be getting worse (right now baobab shows only ~5GB avaliable space). Can you help me find the source of the problem (and ideally also help me solve it :) )?