I have used a certain “online-fix me” (not sure if I’m allowed to promote) website that offers patches for games so you can connect to the official multiplayer servers.
Of course there’s a possibility of getting banned if they detect it, but I’ve played a lot of the Forza games online with this throughout the years without issue.
I realise it’s not strictly on topic for community run servers, but it may be of interest to people in this thread.