HotSpot Automatic (free)

Tested devices can be found under the link: https://android-hotspot.de/en/1300-2/

The app launches the hotspot as soon as the matching Bluetooth device is nearby.

The function can be switched on and off.

No annoying menus. Everything is visible on one page.

Differences between the Pro and Free version

free:

Works with only 3 Bluetooth devices

Pro:

Works with unlimited Bluetooth devices