I think one of the best alternative (that is still free) is actually github pages. The problem is that the contribution model is not trivially solvable via permissioning - the owner of the github page has to approve (the PR changes).

Ideally, what would be best is if there's a set of github action that would automerge changes from a list of approved contributors (who would first fork the page, make the edits and submit a PR). This set of github action would need to be a turn-key setup, without needing much technical knowledge (so that the laymen can do it).