Contributing to open source. It's a tricky one. Supporting open source with money, via a non open source alternative is also tricky, to some. Which is why we looked into alternatives.
If you have a liberapay account for your server, or just for yourself as a contributor to mastodon, you can join the mastodon community on liberapay (linked below).
If you don't have one you can make one, and easily connect with your mastodon and GitHub account. Liberapay are also on mastodon themselves.
I think it can be useful to look at alternative revenuestreams other than just relying on patreon, for those users who may prefer one over the other. As for Mastodon,
I am not abandoning Patreon by any means but if you previously had qualms with Patreon as a proprietary platform, Mastodon now has a team on Liberapay: https://liberapay.com/Mastodon/
I also have a personal account that some people already pledged to before I signed up, I don't know how to deal with that, but here you go (it's linked from the team)