Oh I see, there was some contradictory information on your opening post and I’ve misread that information.
So, you went from Sync3 1.0 to 3.0, Android Auto did not work.
Then you upgraded to 3.4 using Cyanlabs, and it still does not work.
I’m not that sure if that “interim version” applies here, it’s for sure an issue for some users that went for Sync3 3.0… But again, does that apply to 3.4?, I’m not sure to be honest.
As you already know, there’s no way to go back to anything prior 3.2, so you are stuck here.
If you have already master reset and performed basic troubleshooting, I would try getting rid of that “hub not supported” message. That generaly prevents Car Play from working, but usually Android Auto should work… Not always of course, but usually it works…
So that’s what I would do next, replacing the hub.
Check this thread for reference → Media Hub, CarPlay Compatible - 2015-2020 Ford/Lincoln - SYNC 3