Since we are adding ext.uls.eventlogger conditionally this only shows up in the tests. ContentTranslation has the same issue btw.

Conditionally based on what? If it unconditionally registeres modules that depend on modules that only exist conditionally, that sounds like a bug that is not limited to a test suite, but a genuine bug.

Alternatively, it sounds like maybe a dependency isn't installed there (EventLogging?)

EventLogging is optional dependency. ext.uls.eventlogger is declared unconditionally but only added if event logging is enabled. schema.UniversalLanguageSelector is added conditionally if EventLogging is present, as it depends on that extension.

Please look at other extensions for usage examples. One aspect is that schema modules should typically not be depended on directly, especially if the dependent module is loaded directly on a page.

This was fixed by rEULS00349ab0ebf84505fd388fd5e2895a8bff41195f where the bug number was not included by mistake.