My monitor resolution is 3840 x 2160 which is the default for my Windows 11 Dell system. Yes, I do get the flickering in full screen as well. It is not a problem since I can use a lower resolution in the game settings and it works fine.
Ok, I figured out what was causing the flickering...it was the GPU. My laptop has two GPUs: an Intel UHD Graphics 620 and a NVIDIA GeForce MX 130. The Intel GPU was the default for the game. When I changed it to the NVIDIA GPU the performance improved and all flickering stopped.
