I have a dual monitor setup on my Mac Studio--a 4k Dell, and 5k LG. Yesterday I returned from shopping and found a pop-up saying that the LG was not operating at its optimum 5k resolution. I went to the System Settings/Monitor pane and found that there was no 5120 x 2160 setting available, even after selecting Show all resolutions. I tried different options there, and suddenly, my system was unusable if the LG was turned on. See a movie (Apple Forum censored it) at https://www.dropbox.com/s/wm29vkf4bxpcfdp/PA280242.MOV.zip?dl=0

I tried everything:

• Reinstalled Ventura
• Swapped Thunderbolt (TB) cables
• Tried the port in my OWC Thunderflex 8
• Switched the ports on both the Mac and LG
• Rebooted with just the LG on (same issue occurred)
• Reset the LG to factory defaults.

If the LG was on, it was impossible to use the Mac Studio. The LG is off for 10 s, on for 0.5 s, off again, and so on. When this occurs, the Dell loses its display whenever the LG flashes on.

I finally was able to get the LG to work using an HDMI cable, but that limits resolution to 3840 x 2160. If I try this resolution, The displayed things on the LG are squished vertically; The set display scaling options that was on Monterey seems to have disappeared.

Many other things are also broken:

• The mouse focus while trying to label tracks using Audacity is lost.
• The Today Pane on Thunderbird no longer resizes—the pane is either 1/2 the app width, or not displayed.
• Multiple apps say they are corrupted. Some eventually start.
• Apple support said that They could not see my screen using Ventura.

Grrr.