Today, my system froze, and I was not able to use Ctrl+Alt+F2 to open a terminal screen or reach it through ssh. When I rebooted, I found a kernel oops reported in that session’s system log. So far, this has only happened to me once.
As it only happened once, I would simply wait if it happens again - chances are that it does not. I also had a kernel oops in amdgpu some weeks ago and that did not reappear since then.
That said, your BIOS is 1,5 years old - it does not hurt to update that.
With atril there was a segfault. Maybe you can try another PDF viewer?
Are you using wayland? Has this problem occurred under x11?
I use Atril as my PDF viewer, but I didn’t have it open when the freeze happened.
I am using X11, not Wayland.