I just upgraded to Fedora 29. Text scaling slider is gone, now you can only pick between 100% and 200% scaling. Cant understand what would drive this "simplification"
More seriously, I dealt with this trying to run a Linux VM on a Surface Pro a couple of years ago. I don't remember which distro, but 100% and 200% were the only UI scale options.
Surface Pro's native scale in Windows is 150%, and the solution to match that in Linux ended up being to scale it to 200% and then set up xrandr to scale it back down to 75% of that.
Not exactly a clean way to handle it. I'm pretty sad to hear that's still the state of things.
Though they did eventually do a fractional scaling thing with 3x scaled down, which still feels clunky to me but at least you don't have to configure it yourself in two different places one of which is a command line.
Like, okay, make an easy mode the default. But allow for that complexity to exist without completely writing full extensions for basic functionality.