_IF_ the version of phpmyadmin which Bookworm ships doesn't work with
the version of PHP which Bookworm ships, that's at a minimum a
packaging bug. But that would be an awfully obvious one that a lot
more people should already have run into in that case, so I'm
reluctant to assume that that's the problem. I'm more inclined to
believe that maybe you're somehow running a non-Bookworm version of
phpmyadmin which for whatever reason doesn't work with PHP 8, or for
some reason your installation of phpmyadmin is being run through a
different version of PHP. Buster and Bullseye were both PHP 7.x; which
could help explain why it worked there but not after you upgraded to
Bookworm.