It seems to not be so much of a 4k@60Hz problem as a "this should just work" problem.
> The first thing I did—which took almost 30 minutes—was try to figure out how to get 4K (at 30 Hz—the Pi can't output 60 Hz over its HDMI connection) working with a consistent font size across all the applications and system controls.
> The settings in the Appearance preferences seemed to apply to some window chrome and buttons, but not internally in applications. So, for example, the File Manager's main window had readable text after I increased the font size at 4K resolution, but in order to make filenames and other listings readable, I had to go into the File Manager's settings and increase the font size there.
> Same for Terminal. And Chromium. And... you get the idea.
What a heck of a thing to have to worry about in 2020.
The stupid thing is that I think this might actually have regressed in Gnome/GTK+ over the years due to them being more focused on Wayland and semi-intentionally breaking the old X11 DPI code.
> The first thing I did—which took almost 30 minutes—was try to figure out how to get 4K (at 30 Hz—the Pi can't output 60 Hz over its HDMI connection) working with a consistent font size across all the applications and system controls.
> The settings in the Appearance preferences seemed to apply to some window chrome and buttons, but not internally in applications. So, for example, the File Manager's main window had readable text after I increased the font size at 4K resolution, but in order to make filenames and other listings readable, I had to go into the File Manager's settings and increase the font size there.
> Same for Terminal. And Chromium. And... you get the idea.
What a heck of a thing to have to worry about in 2020.