Looks like I may have figured out my screen flickering bug that activates on session lock: only happens when the monitor is set to 144 Hz so it looks like a bug in the compositor. Will open a ticket when I get the opportunity now that I know what’s causing it. I set the refresh rate to 60 Hz yesterday (while leaving variable refresh rate enabled) and, today, the flickering never materialized. Will keep monitoring it for a few days before I open the ticket just in case it comes back, though.