I have a Librem 15 (running Pop_OS 20.10/Heads) and a Librem Key. Heads works remarkably well. I haven’t gotten the Librem Key set up to unlock my LUKS partition yet (the script provided by Purism doesn’t seem to work with modern LUKS configuration schemes. I’m working on that, though, and will post updates when I get things updated).
However, I’m having a problem with GDM - It frequently takes between 2-15 unplug/replug cycles for the Librem Key to be found. It ultimately WILL be found, so I know that my configuration vis-a-vis SCDAEMON and UDEV seems to be correct. I’m not using this key for anything other than laptop authentication - I have apps on my phone and watch for HOTP/TOTP.
Try pkill scdaemon or pkill pcscd and try plugging it back in. I’ve had to do this on a Fedora system to get my Librem Key recognized, it should work the next time you plug your key in.
I’d messed with this for two weeks and couldn’t figure out the issue. A little more research this morning indicated that pcscd could cause a contention issue, and I’d had a Yubikey (with software) installed on this laptop at one point. The Snap install of the Yubikey Manager also included a different copy of pcscd which I’d missed when I tried to uninstall all of the Yubikey stuff.
After yanking that copy of pcscd out, my Librem key is working the first time every time.