Comment # 2 on bug 1234724 from Felix Miata

BTRFS is rather demanding compared to reliable and trusted older filesystems. I
don't use it. I've stuck with EXT4 for / and separate /home/. The following is
from just one of more than 80 current TW, Slowroll and 15.6 installations here,
with / as small as 6.4G, and only two with more than 8G for /:
# pinxi -Saz --vs --za --hostname ### pinxi is devel version of inxi
pinxi 3.3.36-15 (2024-12-17)
System:
  Host: hp750 Kernel: 6.4.0-150600.23.30-default arch: x86_64 bits: 64
...
  Console: pty pts/1 wm: kwin_x11 DM: XDM Distro: openSUSE Leap 15.6
# free
               total        used        free      shared  buff/cache  
available
Mem:         7994052     1011860     6627088      153336      757588    
6982192
Swap:         787148           0      787148
# df /
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sda21       8042140 3745744   3878950  50% /
# ls -rtgG vmlinuz-* | egrep -v 'cur|prv|-s1'
-rw-r--r-- 1 14076832 Jan 19  2024 vmlinuz-6.4.0-150600.4-default
-rw-r--r-- 1 14181408 Mar 18  2024 vmlinuz-6.4.0-150600.10-default
-rw-r--r-- 1 14189408 Apr 22  2024 vmlinuz-6.4.0-150600.16-default
-rw-r--r-- 1 14191584 Jun 12  2024 vmlinuz-6.4.0-150600.21-default
-rw-r--r-- 1 14181152 Jun 19 07:43 vmlinuz-6.4.0-150600.23.7-default
-rw-r--r-- 1 14198912 Oct  2 05:24 vmlinuz-6.4.0-150600.23.25-default
-rw-r--r-- 1 14166080 Dec 10 06:34 vmlinuz-6.4.0-150600.23.30-default
#
Thus IMO, 40G ought to be qualified.