Linux support for HiDPI is not great. GTK3 apps are scaled appropriately, but GTK2 apps are not, and there are still quite a few of those, like GIMP. Such apps are displayed ridiculously tiny on a 4k display with unreadably small text.

I've heard that if you use Wayland, these older apps get pixel scaled up, but most Linux distros have spotty support for Wayland, so getting it running can be labor intensive.