Earlier quoted context omitted.
If using Gnome, only use integer scaling. 100%, 200%, 400%. KDE will have working fractional scaling for the DE and apps using QT and there you can adjust a slider to a % you like.
See but that's exactly the thing, on Mac you can just pick a scaling and every scaling option looks flawless across the board. Integer scaling is silly for me: it's either huge or tiny. Yes, KDE does it better and with Wayland you can also do fractional scaling. But the original point stands: it sucks on (most) linux and works flawlessly on Mac.
Not really, if you have a discerning eye.
Any non-integer resolution on macOS is rendered at twice that resolution, and then raster-scaled down and anti-aliased. So, if you have MacBook with a 2560×1400 display and you select any other resolution besides that and 1280×800 (exactly half), the desktop render will be raster scaled.
To be fair, it works better than Wayland's previous behaviour because of the 2× rendering factor, but you can absolutely still see scaling artifacts if you look for them, and I certainly do. Ringing around text in a dark-mode editor is especially obvious.
The only OS that has gotten HiDPI right is Windows.