Since a few weeks, my #debian #bookworm system was no longer able to build the initrd.img for new kernels. This morning it couldn't boot at all with a recent kernel (it did with an older one), so I found the time to look into it: it seems that the problem could have been related to the fact that my system still had split /usr; I've installed the #usrmerge package and now the initrd.img has been built.

wiki.debian.org/UsrMerge
salsa.debian.org/md/usrmerge/r…
bugs.debian.org/cgi-bin/bugrep…

now rebooting, wish me luck :D