This is a limitation imposed by Apple out of security concerns. The following trigger types in Shortcuts personal automations cannot be run automatically:
- Arrive / Leave / Before I Commute
- Message
- Wi-Fi
- Bluetooth
If you make a personal automation with any of those triggers, it’ll first show a notification on your lock screen that you must accept to continue running the actions. I agree that this kind of defeats the purpose of an automation, since it’s no longer automatic. Only thing that can be done is send feedback to Apple, as the limitation is on their end.
The best alternative would be to use an iBeacon which typically costs only a few bucks. Keep it plugged in to any of your cars USB ports, and then when the car gets powered on it’ll start transmitting via Bluetooth. Once your phone sees that signal and sends a webhook to Home Assistant which runs your gate scripts. I use the Geofency app to do this but it’s also supported in OwnTracks.
I’ve been doing this for two years now with Geofency (to determine car presence) and it works very well.