You absolutely can use the Blastem emulator. You can also use BlastEm core with Retroarch as well but if things are working good with the BlastEm emulator itself then just stick with it.

Anyway the discord for SoR in general is tied to Brawlers Ave. I'm under the impression the ones in charge of that discord don't want people publicly posting the discord invite link so I'll send it your way privately. Some steps have to be followed first after you enter if you want to use the discord though.