Extra monitor won't sync under kernel 6.2 but OK on 5.19

I have a Dell XPS 17 9700 with dock driving 3 monitors:

  Monitor-1: 1366x768 (old viewsonic LCD)
  Monitor-2: 5120x1440 (big and wiiide)
  Monitor-3: 1920x1200 (laptop LCD)

Under kernel 5.19 all is well, but under kernel 6.2 (under Mint Vera or Victoria) the Monitor-1 viewsonic won't sync properly:

I think the whole image is there, but just squashed up with trailing junk.

I still have my 5.19 kernel available since before upgrade so I can still work, but I'm not sure where to look to find what to blame for this. Do I need to manually specify a modeline?

Ubuntu 22.04.03 booted from USB has the same problem:

Ubuntu 23.10 with kernel 6.5 below works just fine:

And so fixed on Linuxmint 21.2 with:
sudo apt install linux-oem-22.04d

https://ubuntuhandbook.org/index.php/2023/08/linux-kernel-6-5-released-how-to-install-it-in-ubuntu/