It’s fairly simple to set one up for any server. The Mastdon API call is documented at apps API methods - Mastodon documentation
You just POST your app’s name and a redirect URI.
It responds with your client ID and secret.
From there you do the normal OAuth dance.
So, if this were a supported Auth0 product, I’d expect to see:
Sign in with Twitter
Sign in with Mastodon
Sign in with Facebook
Click on Mastodon should show a prompt saying
What’s your Mastodon server? __________
And, from there, Auth0 can create an app on the fly and proceed in the same way as signing in with Twitter.
Thanks for the added info. Yes, that makes sense, but isn’t currently possible with the existing custom social connection implementation. You would need a different authorize and token URL for each server, right?