The test is known to fail on Ubuntu 18.0.4 and Ubuntu 20.0.4 and only on .NET 5 and higher. While this makes it highly likely the issue is related to the ICU integration in .NET, changing to NLS seems to have no effect on the problem.
More investigation is needed, but due to the fact this is only returning display text for a culture it doesn't seem to be a blocker for releases at this point.
ICU4N.Dev.Test.Collate.CollationServiceTest::TestRegisterFactory() is failing on Linux due to the
Collator.GetDisplayName(UCultureInfo)method not returning the correct name for a customUCultureInfoinstance registered withCollator.GetDisplayName().Impact
The test is known to fail on Ubuntu 18.0.4 and Ubuntu 20.0.4 and only on .NET 5 and higher. While this makes it highly likely the issue is related to the ICU integration in .NET, changing to NLS seems to have no effect on the problem.
More investigation is needed, but due to the fact this is only returning display text for a culture it doesn't seem to be a blocker for releases at this point.