If they offer an oauth login API it should be pretty easy to implement.
If you're up to the challenge just check the existing auth extensions (For example Patreon login by Flagrow, where both the extension and oauth wrapper were written for it)
And even if no oauth is available you might be able to pull something up. For example Flagrow Telegram login has a very exotic process, yet it works flawlessly with Flarum login.
