@jeff okay this is probably a unpopular opinion but fuck it: I wouldn't mind to see ads if this means it would help to run the server. Mastodon should implement ads with a easy opt in/opt out model (for the users) that server admins can choose to use on their instance.
And maybe a easy one click donation implementation in the official app over the app store. Like I heard from a friend who works on apps: "With every additional click you will loose people that are willing to pay."