I’m using OpenBSD as a daily desktop. The main motivation is that it’s a complete system instead of several projects. So you got simpler userland tools as the kernel interfaces can be easily adjusted.

Also the subsystems are way simpler (packet filtering, sound, network management). Linux is full choke of abstraction which aim to serve a huge range of devices. And I truly believe that there should have been a bifurcation somewhere.

Most software are easy to port around, but there are some that relies on linuxisms (udev) and some on glibc-isms, which can require some patching. Some of the pains I encountered are about device files (usb) and the fact that openbsd relies on root a bit more (mounting with fuse).

You can read the “Absolute OpenBSD, 2ed” book, published 13 years ago and almost everything still holds. You can even read the “Design and Implementation of the 4.4BSD” and still have a good understanding of the OpenBSD design. Linux is chaotic land compared to that.