This "fractional scaling" might be a problem of Wayland and/or Gnome, but it certainly it is not a problem of Linux or of X Window System.
In any non-stupid graphics environment you need just to set an appropriate value for the dots-per-inch parameter, which will inform all applications about the physical size of the pixels on your monitor (allowing the rendering algorithms to scale arbitrarily any graphic elements).
Any non-stupid application must specify the size of the fonts in typographic points, not in pixels. When this is done, the fonts will be rendered at the same size on any monitor, but beautifully on a 4k monitor and uglier on a Full HD monitor.
The resolution of a Full HD monitor is extremely low in comparison with printed paper, so the fonts rendered on it are greatly distorted in comparison with their true outlines. A 4k monitor is much better, but at normal desktop sizes it is still inferior to printed paper, so for big monitors even better resolutions are needed to recreate the same experience that has been available for hundreds of years when reading printed books. A 4k monitor can match the retina resolution only for very small screens or for desktop monitors seen from a great distance, much greater than a normal work distance.
Similarly, any non-stupid drawing applications must not specify any dimensions in pixels, but in proper length units or in units relative to the dimensions of the screen or of the windows, and then the sizes will be the same everywhere, but all graphical elements will be more beautiful on a 4k monitor.
This was already elementary knowledge more than 30 years ago, and recommended since the most ancient versions of X Window System and MS Windows. I do not even know when this modern "fractional scaling" junk problem has appeared and who is guilty of it.
I have switched to using only 4k monitors with my desktops and laptops, on all of which I use Linux (with XFCE), about a decade ago, and during all this time I never had any kind of scaling problems, except with several professional (!!) applications written in Java by incompetent programmers, which not only ignore the system settings, so they show pixel-sized windows and fonts, but they also do not have any option for choosing another font or at least another font size (so much for the "run anywhere" claim of Java).