Useful discussion, but I take issue with this statement: "Linux still has problems with "fractional" scaling modes like 125 percent and 150 percent, which was what the old Framework screen usually looked best at."
Gnome on Wayland may still require weird workarounds because Gnome is written by people who hate their users, but on Plasma desktop partial scaling just works, including different scale factors between different screens.
Can confirm. For really good fractional scaling and other modern display tech to really shine on GNU/Linux you need to use KDE Plasma desktop. Others are still catching up.
Gnome on Wayland may still require weird workarounds because Gnome is written by people who hate their users, but on Plasma desktop partial scaling just works, including different scale factors between different screens.