I have an M1 Mac and an LG HDR 4K external monitor. I had this problem (blurry display at everything other than the highest resolution, which is too small for me to read) after updating to Ventura.
Downloaded this free tool: https://github.com/waydabber/BetterDisplay
This solved the problem for me. I switched to 1920 x 1080 resolution and it now looks perfectly sharp again. Great tool that allows further configuration as well, including easily setting the brightness of my external display.
Downloaded this free tool: https://github.com/waydabber/BetterDisplay
This solved the problem for me. I switched to 1920 x 1080 resolution and it now looks perfectly sharp again. Great tool that allows further configuration as well, including easily setting the brightness of my external display.