Another option you may consider, if you’re already open to using Apple technology, is a MacBook. It would be like having a Mac mini with a built-in battery. I’m not sure if you already have batteries in your setup, but all of Apple’s current lineup of laptops are basically equally as performant as their desktop options right now (excluding the super high end stuff like the Mac Pro).
Ruffle is one of the most important pieces of game preservation currently out there, and it warms my heart to see it constantly improving!