This is as of the latest unstable packages before today's stable sync, and has been happening since sometime after last Friday (2019-12-13). Changing the xrandr mode of my monitor fixes the problem, as does restarting lightdm and rebooting. I am on Solus Budgie, using an AMD RX 480 with mesa.
To clarify, by "long suspend", I mean the screen is blurry when I leave my computer suspended overnight. I don't believe it's a hardware problem, as I dual boot on this machine and Windows has not exhibited the same behavior.