Freexian 
We have published a blog post about the completion of /usr-move transition in Debian.
It covers why it was needed after /usr-merge transition and the work done to resolve the issues during the #trixie release cycle.
Read more at https://www.freexian.com/blog/usr_move/?utm_source=mastodon&utm_medium=social
Debian's /usr-move transition has been completed
By now, the /usr-merge is an old transition. Effectively, it turns top-level directories such as /bin into symbolic links pointing below /usr. That way the entire operating system can be contained below the /usr hierarchy enabling e.g. image based update mechanisms. It was first supported in Debian 9, which is no longer in active use at this point (except for users of Freexian’s ELTS offer). When it became mandatory in Debian 12, it wasn’t really done though, because Debian’s package manager was not prepared to handle file system objects being referred to via two different paths.