I've tried reducing the QHD refresh rate from 60Hz to 50hz and this has been quite stable so far. Fingers crossed...

I've got my new monitor (a Dell U2719DC) and I've been able to reproduce the blanking issue reliably. I think your correspondent is correct that it's related to performance.

I don't currently have access to a monitor but that will be changing soon. If the issue returns with my new monitor (whichever I end up choosing) then I'll check the dmesg log and report back.

In T298#15256, @jeremiah.foster wrote:

In this case;

For the last couples of weeks I have had my Librem hooked up to an external monitor (UP2516D) by HDMI and experience some odd screen flickering. Maybe “flickering” is the wrong word, what happens is that the screen blanks at random intervals for about a second once every few minutes. I have struggled to establish any pattern, my best current guess is that it is correlated with CPU load as it becomes much more frequent once the fan starts spinning. It should also be emphasised that the laptop screen never flickers, I have confirmed this by observing flickering on the external monitor while the laptop monitored remained stable when I mirrored the output. I have investigated this issue on and off for about a week now, with no success, thus I am reaching out to you.