Martin Steigerwald - 27.11.23, 09:16:53 CET:
> Thus will install usrmerge and merge the systems *today*. Better be safe
> than sorry.

Did the merge on this system already.

usrmerge complained about some duplicate udev rules and hwdb from SANE
related package, but after I removed the one from /lib, it proceeded.

As a security precaution I also updated initial RAM disks with

update-initramfs -k all -u

System booted fine.

Thanks again, Lorenzo.

--
Martin