Unfortunately, as there’s no maintainer for the phpMyAdmin package for Debian Buster, it’s not been included in the Debian repos, so the
sympl-phpmyadmin package can’t be installed.
I investigating swapping phpMyAdmin for Adminer, but unfortunately, the feature set for Adminer is too narrow for what’s needed and there is little to no security with it, meaning integrating it safely would be a headache.
As a workaround, I’m putting a guide together on manually installing the current version of phpMyAdmin on Sympl 10.0, and securing it in the same way it was for Symbiosis and Sympl 9.0.
While it’s unlikely the package will turn up in Debian, if a trusted third party repo does appear with the package, it should be able to update the guide and/or rebuild the package.