@pixelfed you might want to consider registering as non-profit entity, or a "Friends of Pixelfed" non-profit that can donate to Pixelfed/you, so users can get a tax break and donate more. Happy to contribute anyway!
One other suggestion: offer a suggestion donate based on some basic usage. I always have a hard time figuring out what's an appropriate donation to a services I like vs when does it may sense to just buy a similar product. This could be useful for server owners.