Using SysRq to collect state of system before reboot

I have a Debian Buster machine that freezes every now and then. No keyboard and mouse inputs are processed, but the screen still shows the login screen. Logs appear to show nothing out of the ordinary, so it feels like i've got to do something to capture more data "in the moment" I want to use SysRq to collect more information before rebooting - what approach should i take?