My long time favorite was Stonerune, quite simple, no bling-bling.
With the last updates it lost functionality, so I tried other UIs like Strange, Ikos and King UI.
The problem is, that I miss the buttons for guild, friendlist etc. in the left upper corner completely, plus there is only one row for combos/spells at the bottom, no matter which options I choose before installing (with AoC UI Installer 3.1.0).
So I deleted the "Customized" folders in both /GUI folders I could find.
It didn't help, I can't install any of the three mentioned UIs.
It looks to me like some parts of the custom UIs where not deinstalled properly.
Is there a way to get a clean default UI?