I agree, sadly a clean API and examples are not as common as they should be. Personally I like how the Nakama SDK is fully up-to-date for Defold. Seems like most other backend services are falling behind, abandoned, or buggy (PlayFab, Steamworks, etc.)
The setup really isn’t difficult, but I do believe that it is probably the #1 blocker for new users. But to be fair, someone who is not willing to learn is probably not a candidate to be making a multiplayer game anyway.