Idea is to allow a bluetooth keyboard to communicate with a device that can't support native bluetooth due to hardware or software limitations.
The simple magic trick is to use a raspberry pi (4 or Zero) in gadget mode, meaninng it's physically plugged into the device via USB to do the keyboard emulation after getting instructions from the bluetooth keyboard thanks to evdev.
- Pair your keyboard to the pi
- Run
sudo ./setup.sh - Reboot your pi
- Enjoy your new "wired" keyboard
Some helpful stuff I used for reference