Yeah I understand the frustration, I had issues setting up ESLint/Prettier years ago and spent a few hours getting the Biome configuration right. Also a monorepo with ~4000 TS/TSX files. If you ever feel like trying it again, make sure that you have "files.maxSize" and "files.ignoreUnknown" set. And be very careful with the "files.includes" list.
It sure would have been nice if biome used a better include syntax. I dislike the new way of doing it in biome 2, because it creates ambiguity and works differently than damn nearly every other tool I use