KDE almost became my default when I was installing probably my first bare-metal Linux distro a few years back - Debian Buster, to be precise - on an old laptop. However, something borked with the network manager installation, so when I tried again, I chose XFCE, which worked (probably by coincidence - I probably just did something dumb the first time) and has been my go-to ever since.
From a programming perspective, I definitely like Qt a lot over GTK, though it’s not like I write GUI applications all the time anyhow.