I’m guessing you need at least a certain RA version, does the Android version matter?
It’s been in RA for quite a long time, so unless you’re using a super-old version, that shouldn’t matter. I don’t think Android version matters, either, aside from actually being able to run RetroArch.
@Jamirus As far as I know you can pretty much install any core on any recent version of retroarch. All you have to do is to download the core from retroarch’s build bot then unzip the zip file so you have a core with .so extention then open retroarch and head to load core then choose install or restore core then navigate to the folder in which you keep the unzipped core file (.so file) and choose it, it’ll install the core. Make sure you download the core according to your system (32bit or 64bit). You can also install unofficial cores this way.