YMMW but I had a really good experience with 2x scaling on a 4k Laptop Screen in standard Ubuntu and gnome. There are still some apps which ignore dpi settings (zoom) or need to be forced to scale (often electron stuff, although you can usually just zoom with Crtl+ there). Otherwise awesome sharp text and fluid.

Fractional scaling seems to be quite a mess, at least in KDE it breaks a lot of layouts.