I'd say Linux directly, since performance would be still better than in Proton. Proton is a gap solution that helps building up user base while developers still

I'd say Linux directly, since performance would be still better than in Proton. Proton is a gap solution that helps building up user base while developers still ignore the platform. I.e. some developers don't care about performance much, so they might rely on Windows builds. But others might care enough to make native versions once they see the platform as a significant target.