The standalone installer only supports SQLite, and I think that is the only option, if we want to keep the standalone installer simple.
It does not matter which database you use for development, the buildRelease will always use sqlite for the standalone installer.
For Linux, I think we provide scripts for PostgreSQL, MySQL and SQLite in the tar archive. I guess for RPM or DEB packages, we should target PostgreSQL only. It is easy to add that dependancy, and nowadays the installers in Linux are clever enough to collect the dependancies.