This is about a solution for issue behind {T7674} on master (KF6), the solution in T7674 was for the legacy kf5 branch only.
On master the new option `AllowedPGPKeyTypes` should support a list of algorithms (same as gpg's --quick-add-key and --quick-gen-key support). This new name ensures that there is no confusion with the old option `PGPKeyType`.
`RSAKeySizes` shouldn't be supported anymore, but it should probably be (optionally) migrated, i.e. `PGPKeyType=RSA` + `RSAKeySizes=NNN,MMM` could be migrated to `AllowedPGPKeyTypes=rsaNNN,rsaMMM`. The old settings `PGPKeyType` and `RSAKeySizes` should be left as-is by the migration so that people trying out a beta version don't break the configuration of their production version.