I also have a computer with NVidia gpu (which turns fractional scaling into an unresolvable problem on Gnome currently, that's why I tried Kubuntu in the first

I also have a computer with NVidia gpu (which turns fractional scaling into an unresolvable problem on Gnome currently, that's why I tried Kubuntu in the first place) and 28" 4K display running Kubuntu and use the display with the Macbook too. Works flawlessly.