Good to see that Mastodon has a 501(c)(3)! Also,, even if not all the board is elected, there's a lot of value in what Wikimedia and Global Voices do, with at least some board seats open to election from staff and the community.
With regular elections, the board gets to see and hear from the evolving set of hopes, concerns, and constituencies that are of interest to the community every time an election arises.