You need a fully custom UI. Manually it’s a lot of work. The strange UI Google Drive link includes one, playable but it’s not fully complete nor up to date: (2023+) STRANGE UI + AOC UI Installer + others ui & 4k
It’s what I started from, nevertheless.
There are a few of us playing at 4k for years now (I have played literal thousands of hours in 4k), but I think we all have our own personal UI at this point.
I updated it by hand (to bring back the missing new buttons/functions) and did a lot of fine tuning to correct the size and position of some things (with the help of @Cappa for the bottom bars and target bars!).
If you watch Henryx youtube or mine, you will see what a 4K UI can look like in AoC. Spreadman has recorded himself playing in 4K too, not sure where he found it but his looks way too small.
edit found a link to spread’s UI: 47.85 MB file on MEGA
Didn’t personally test so I’m not sure if it’s missing anything but should be playable.