The risk of running into this stuff is exactly why I have timeshift take a BTRFS snapshot before upgrading between versions.
First, double check all of your /etc/sources.list and /etc/sources.list.d files to make sure they point to the right versions, and then run the update + (dust) upgrade again. There’s a chance you have an external dependency that’s keeping some packages locked to an old version or something like that.
If all else fails, sudo aptitude reinstall ‘~i’ will reinstall every package on your system. It’ll prompt you to replace tons of updated configuration files, so maybe make a backup of /etc just in case. You may need to install aptitude first (it’s in the normal Debian repos).
If that fails: copy /etc and your home directory to an external drive, dump all installed Debian packages to a file, reinstall Debian, restore the package list from that file, and copy back your config. This would also be an opportunity to make any low level changes to your system (i.e. upgrading the security of your LUKS header, maybe setting up a filesystem with snapshotting, fixing any partitioning mistakes you may have made over the years).