I started playing around with UOX late 90s then with a shorter-lived one called CFuse.
Then I moved to POL where I did some scripting and finally RunUO where I worked on a customised server for a long time until my "great data loss of 2002" where I managed to wipe a disk containing everything I had been working on, among lots of other things :-)
I found a nice timeline of the different server emulators here: https://www.uox3.org/history/timeline.shtml