I have been trouble by a flickering external monitor ever since 11.1, but not before. After corresponding with CalDigit, I followed their list of remediation steps and troubleshooting. They ended up replacing my TS3+ thunderbolt dock, with little improvement. I've tried 3 monitors, connected via DVI-D from Displayport, with an active $33 StarTec cable. I took the TS3+ entirely out of the picture by using an Apple Thunderbolt-to-HDMI adapter. I added ferrite cores to both ends of my 2m Displayport-to-DVI-D cable. I just tried arunprakash94's technique of cutting off gpuswitch for [-b, -c, -a]. I think it helped? There is still a flickering problem that did not occur under prior releases of MacOS. Is it possible that my monitors are all now damaged? My HPZR24w monitor is connected to two different MacBook Pros: 1) my employer's 16-inch late 2019 with 10.15.7 using a $15 WARRKY USB-C to Displayport cable, 2) my 15-inch 2016 with 11.1 via DVI-D. That HP monitor never flickers when driven from the older OS.