I have the same chip in my mini PC (7840HS) and it works fine for me on Linux, but then again I use Arch + Wayland. Maybe you could try a couple of different distros on a Live USB or something (you could create one using Ventoy and then put a few different ISOs on there to play around with). I’d recommend choosing a distro with a recent kernel and updated graphics stack, for eg Arch or Bazzite and see how it goes.
But the artefacts you describe sound more like a hardware glitch to me. Have you tried running the Lenovo hardware diagnostics from the system boot menu? (IIRC you need to press F12 or something to get the menu and then choose the diagnostics mode).