Ubuntu’s font rendering used to be better than every other distro, because they incorporated patches on freetype that were legally ‘iffy’ as to whether they infringed on microsoft’s patents; later whatever exclusivity requirement that there was with those patents expired, and the patches got upstreamed in freetype itself.

So now all Linux desktops are capable of subpixel font rendering, hinting, whatever. But before that, font rendering really was hideous on other distros.