Hi Claire,
I use a (Apple) Thunderbolt (Usb-C type) to connect my PHL 499P9 directly. I also have a Windows Laptop, still working fine with my PHL 499P9 at 5120x1440 in 60Hz. If I connect my Macbook Pro to my external monitor and choose 5120x1440 (which is nativ resolution for this monitor) my monitor screen is scrambled / unreadable. When I tried different settings, I even ended up with having my laptop monitor being scrambled and my monitor working in low resolution...?... weird. My workaround just now is to use 3840x1080 resolution and a HDMI cable with a HDMI to USB-C converter connected to my Macbook Pro, but I have to use the USB-C port on right side to make it work (I normally use a port on the left side for my Thunderbolt-cable). If I use a port on the left side, it flickers to this scramble view a bit.
To me, it looks like there is serious driver issues with Ventura....
I would be thankful if you can help!
Cheers //Jan