I run my laptop on the unstable channel, and I use a Bluetooth Low Energy keyboard. It seems that recent changes cause my keyboard to no longer connect. Bluetooth works fine and sees new devices but not my already-paired keyboard.
I did some upgrades without rebooting and this morning a thermal event forced a reboot and then I noticed. Of course, thanks to NixOS being super awesome, I could just boot previous generations and I found that the breakage happens sometime between 21.03pre246062.420f89ceb26 and nixos-21.03pre250162.34ad166a830.
The comparison is https://github.com/NixOS/nixpkgs/compare/420f89ceb26...34ad166a830 but GitHub crashes on that
I don’t have time right now to investigate further, does this ring any bells for anyone?