If I’m going to do that I’d suggest nos.social for the app but either the user still has to install a browser extension and configure it. That’s a lot of steps for nontechnical users.
Does it have to be browser extension? Ideally, cutting out steps, login happens over nos.social and on desktop protest.net they scan a QR code that logs them in? (I’m not technical so don’t know if this would be possible)