For some reason my Wifi Launcher/HUR connection seems to have mostly resolved itself. I'm running Android 12 on a Samsung S10+ and a Chinese generic Pumpkin brand head unit (Android 10 I think). These are the ducks to get lined up: Before switching off the ignition, exit HUR on the head unit. HUR can't be running when powering on. HUR needs to be in 'Start Wifi automatically' in HUR settings-> Connectivty. When ignition comes on, HUR should call the phone to start up Wifi Launcher. The red 1 should appear on the Wifi Launcher icon. If all goes to plan, the connection should be established and AA starts up.
If it doesn't go to plan, some things to try:
Open Wifi Launcher and go to advanced at the bottom to manually start Wifi Launcher if it doesn't start up when the ignition is switched on.
Enable 'Add Force Connect button in Notifications', under advanced too. This is the screen that you pull down from the top of the phone's screen that shows your messages etc. If the above doesn't get the phone to connect automatically, open up this screen, tap on 'Wifi Launcher is looking for car screen' and tap on 'Force Connect'.
If your connection fails after a short time repeatedly, open up your Bluetooth. Mine was opening a phone connection and an audio connection to the head unit simultaneously. If this is happening, I have to disable the Bluetooth audio connection manually in time before the head unit drops out.
Recently I had trouble with phone calls not being routed through the head unit, instead remaining on the phone. I discovered that the Bluetooth connection for calls has disengaged. When I re-established that, it's been doing the right thing again.