Not so well on displays with non-integer scale factor (1.25-1.5x).

I've somehow managed Plasma & Qt apps to have acceptably sanely sized windows decorations and widgets, but failed to e.g. teach the browsers to calculate sizes correctly (e.g. make a block with `width: 50mm` to have correct size).

Biggest GNU/Linux problem is having way too much of the completely different solutions for the roughly the same thing that can't interoperate with each other.