I've talked with both the internal team and the Debian maintainer of
the WSL image. This is a WSL 1.0 specific issue, and there's not much
we can do in usrmerge about it, as it's related to the underlying
filesystem that we can't touch anyway.

The Debian stable WSL image in the store will be updated shortly to be
merged-usr out of the box, so this won't happen again for new
installations, and on upgrade to bookworm it will be a no-op. Older
installations on WSL 1.0 will have to remove and reinstall, unless a
workaround is found, but for that please use the upstream bug tracker
as here we really can't figure out what the problem is.

Also please note that it would be a good idea to just move to WSL 2.0
for all use cases at this point.

Hence, setting the forwarded address and closing.

-- 
Kind regards,
Luca Boccassi

Setting up usrmerge (33) ...
mv: cannot move '/lib/x86_64-linux-gnu/security' to '/usr/lib/x86_64-linux-gnu/security': Permission denied

FATAL ERROR:
mv --no-clobber /lib/x86_64-linux-gnu/security /usr/lib/x86_64-linux-gnu/security: rc=1

Setting up systemd (252-2) ...
systemd-machine-id-setup: error while loading shared libraries: libsystemd-shared-251.so: cannot open shared object file: No such file or directory

sudo mkdir -p /usr/lib/x86_64-linux-gnu/security
sudo chown root:root /usr/lib/x86_64-linux-gnu/security
sudo chmod 755 /usr/lib/x86_64-linux-gnu/security

FATAL ERROR:
Can't rename /lib: Permission denied at /usr/lib/usrmerge/convert-usrmerge line 286.

dpkg: warning: This system uses merged-usr-via-aliased-dirs, going behind dpkg's
dpkg: warning: back, breaking its core assumptions. This can cause silent file
dpkg: warning: overwrites and disappearances, and its general tools misbehavior.
dpkg: warning: See <https://wiki.debian.org/Teams/Dpkg/FAQ#broken-usrmerge>.

Preparing to unpack .../archives/usrmerge_35_all.deb ...
Unpacking usrmerge (35) ...
Setting up usrmerge (35) ...
mv: cannot move '/lib/x86_64-linux-gnu/security' to '/usr/lib/x86_64-linux-gnu/security': Permission denied

FATAL ERROR:
mv --no-clobber /lib/x86_64-linux-gnu/security /usr/lib/x86_64-linux-gnu/security: rc=1

You can try correcting the errors reported and running again
/usr/lib/usrmerge/convert-usrmerge until it will complete without errors.
Do not install or update other Debian packages until the program
has been run successfully.

E: usrmerge failed.
dpkg: error processing package usrmerge (--configure):
 installed usrmerge package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 usrmerge
E: Sub-process /usr/bin/dpkg returned an error code (1)