Been using NoPhoneSpam. While it won’t automatically block any numbers, it will cancel incoming calls not matching its filters. Only issue is that, some times, it takes a few seconds for it to recognize not passing calls, but I think it happens when the phone is under a higher load and the system starts lagging a bit, like when downloading bigger files and playing games.

Never saw it before, but going by its description now, it’s the “GNU version of the Firefox browser”, so I would presume you can import everything you could between two Firefox installations, like whole profiles and favorites back up file.