From page:
https://wiki.debian.org/Teams/Dpkg/FAQ#Q:_Does_dpkg_support_merged-.2Fusr-via-aliased-dirs.3F
If you have a system that has been installed recently (since Debian buster) or switched via the usrmerge hack, you might want to consider using the dpkg-fsys-usrunmess program (but beware that it should not be used in systemd's emergency mode) or reinstalling. For further information see Teams/Dpkg/MergedUsr(https://wiki.debian.org/Teams/Dpkg/MergedUsr).So every recent Debian installation is broken?
If so, why no one talks about it?