Just in case anybody still has USB trouble despite using @AudioGod's mapping, this might be the cause:
Do you use any USB-C Dongles/Docks with your MacMini? I had the same issues when using a Dell USB-C Dock with Ethernet. The interferences made the Bluetooth drop randomly once or 10 time/ a day.
Switched to a Thunderbolt 3 Dock and all problems went away...
Just tested it again with 29.
Now it works as expected: Insert headphones and the line out is muted, remove the headphones and line out plays again.
Sorry for the confusion!
But now we know that with 28 you can leave the headphones plugged in an switch in the settings!
I have a Pro rev. 1.0 (non-WIFI) and I can confirm that the rear middle bottom output is not putting out any sound, no matter if the headphone jack is in use or not.
But don't worry I hooked up my FiiO which has a much better sound anyway...
Thanks again for making my machine great again!
Runs perfectly smooth so far!
One last mini hiccup: My sound output "Line out" in the back is not working with alcid=29. Only the headphones in the front work.
Anybody got the rear output working? I had alcid=7 in my previous config, but then the front headphone output would not work.