In #21935 (comment) it was pointed out that neither test-nss-hosts nor test-nss-users is run automatically on a regular basis. To address that #21946 was opened where the tests failed under UBSan as expected. That PR was closed in favor of #21778 where the tests keep failing on Ubuntu CI/Semaphore CI because systemd is built with nss there but libnss-* packages aren't installed when the "unit-tests" test is run. It would be great if it was possible to either fix the debian package or skip the test upstream. Turns out all those "deny-list-ubuntu-ci " files affect the "upstream" tests only (which I already turned off in that PR).

cc @mbiebl @bluca