edit: sorry, I just saw this bug is already reported https://github.com/modxcms/revolution/issues/15328
With MODX 2.8.0 and 2.8.1, the filemanager can’t open folders anymore that have umlauts like äöü in the name. I tried it with multiple installations on different server including modx cloud. It did work until 2.7.3.
I also upgraded one site from 2.7.3. to 2.8.0 to test both version in the same environment.
It is still possible to create folders with names like “test-ä” but that’s it. The css hover effect does also not work for these directories. I tried it with multiple browsers too.