It definitely can be loaded into UMBs. You need about 65k free UMB available, though. Check what happens when typing

LH ULTRAMID

when EMM386 is ON.

If you use EMM386 or another VCPI manager I recommend to load Megaem instead which includes Ultramid functionality. It takes up only 768 bytes.
If you use Himem only there are no UMBs available, thus you can not load ultramid high.
However if you use UMBPCI with a supported chipset and Himem you can make UMBs available and load Ultramid to high memory.

I do use EMM386, but when I try to load megaem I get an error message about "EMM incompatability problem". It recommends I use EMM386.EXE, 386MAX or QEMM386... Yeah well... 😜
I clearly won't be able to load Ultramid high though, as there's nowhere near enough free umb. I guess it doesn't matter as long as I don't actually encounter a stubborn game that needs 600KB base memory and Ultramid at the same time 😜

Thanks for the tips anyway. 😀

This problem is well known (I have written about it here in the forum already) and a result of having too much RAM (which means 64 MB or more) and using HIMEM+EMM386.
A simple workaround is to use an older version of himem.sys like 2.77g that limits XMS to 16 MB. Having just 16 MB available is for DOS games no issue.

With QEMM386 it works, regardless of how much memory you have.

I suppose I could just take out one stick on memory and run my system with 32MB if that helps, but we'll see if I actually run into any situations where Ultramid eating up tons of base memory really cause problems. Only a few games so far have required Ultramid to be loaded (Tyrian, Under a Killing Moon and The Pandora Directive), but I expect more could pop up in the future.

Yes, there are some more around 😀

EDIT: See the attachment. The list is quite long. Memory requirements are not given, though.