This morning, I was using my Librem 5 running PureOS amber with a little USB Type C hub into which I had plugged a Twiddler3 (which appears logically as a standard USB keyboard and mouse) and a Logitech USB mouse (the “mouse” functionality in the Twiddler is rubbish, hence a second actual mouse for actual mousing, in this instance). This normally works fine, and it was working fine.
Finishing up what I was doing, I noticed that there was an update available for phoc, so I pressed the “Restart & Update” button. Upon rebooting, I found that the unlock keypad would not appear and the phone ended up powered off. According to /var/log/apt/history.log, phoc was updated from 0.7.1-1~pureos1-amber1 to 0.8.0-1~pureos1-amber1.
After some messing about, I found that any time I connect either one or both of my USB mice in any combination, whether directly or through the hub, using any of my cables or adapters, the screen goes black. After the screen goes black, somewhat at random, one of two things happens: either the phone crashes and powers off and sits there powered off until I power it on again, or the screen stays black until the mouse is unplugged, then the UI reappears and I can continue using the phone.
This only happens with mice. If I plug in a USB keyboard, the keyboard works fine, but as soon as I add a mouse the screen goes black. I also tried a USB flash drive, which worked fine too. It makes no difference whether I connect an HDMI monitor or power input to the hub. So it seems like this is a mouse problem.