misskey and micro.blog from @manton both support client registration for clients like this by simply providing a website url
it's called "indieauth" (displayed in the login info row, otherwise falls back to mastodon-style app-creation-based registration)
there is a newer emerging standard for dynamic client registration, but no one supports it yet - I'll add it when one does!
micro.blog doesn't support C2S follows via the outbox yet, but we can fallback to the micro.blog api here