Testing [1] Works in Firefox, Helium and Curl but I do not have Chrome or Safari to test with.

[1] - https://_test.nochan.net/

This only works because it’s a wildcard certificate. Since 2019, TLS certificates must not be issued for names containing underscores <https://cabforum.org/2018/11/12/ballot-sc012-sunset-of-under...>.