Hi, I have a XFX 5700XT and a LG 34UC79G 34" Ultra Wide Display with a resolution of 2560x1080.
After installing the 2020 20.2.2-mar5 driver my screen was maxed out at 1280x1024 and 75hz.
I could only change it when I re-install the driver. After a reboot it was back to this weird resolution.
I DDU´d in safe mode, installed new without i-net connection, installed / deleted monitor driver etc. Nothing helped.
Resolution (in case somebody has the same problem)
check the on screen menu of the monitor. In "General" you have a setting called DisplayPort 1.2 (Enabled / Disabled) I switched it to off and it worked again...
I´m back at 2560x1080 at 144hz.