Fedora. I’ve been using it since Fedora Core 1 and was mostly RedHat before that. I don’t have time to muck around with my desktop and Fedora almost always just works. I’ve had too many problems with Ubuntu and Suse and friends. And while I like Arch and Debian and others, I just want my desktop to be point and click. My days off tinkering on my desktop are long gone. Kids, house, work, wife, grandkids, other hobbies keep me busy. I save tinkering for my selfhosting adventures.
Not all TerraMaster units. I happen to have one that can’t replace the OS.