If you want to try the firmware be warned that it is kinda hard to roll it back and you run risk of loosing the connection to your hardware dongle. Steam offered a tool to flash an official image, but there was a bluetooth enabled firmware that you can't get to work with it so easily. I spend a day rolling mine back a while ago and since then there were many steam client updates so I assume it to be harder now.

I documented the whole process half heartedly, dumped the server addresses of the firmware images (from the steam binaries) and archived them (for me). I didn't yet share the whole process since it is only half finished and I didn't completely reverse engineered the pairing process (for the controller to the dongle) just yet (and I probably won't since mine works).

If you want to roll it back you have to download an old steam installation to do the pairing.

If someone would finish the open source firmware that would be great though. I have neither the energy nor the time