Seems this is an issue with some Acer displays.
https://community.amd.com/t5/graphics-cards/rx-6600-xt-input-not-supported/td-p/527234
My son and I both have Acer displays and have not experienced this issue however ours are 1440p resolution.
Ryzen R7 5700X | B550 Gaming X | 2x16GB G.Skill 3600 | Radeon RX 7900XT
Ryzen R7 5700G | B550 Gaming X | 2x8GB G.Skill 4000 | Radeon Vega 8 IGP
Ryzen R5 5600 | B550 Gaming Edge | 4x8GB G.Skill 3600 | Radeon RX 6800XT