IRC was too janky for widespread use... Everything else that has come after it hasn't been able to reach the "network effect". Too many options, too many half finished projects. Lots of missed opportunities.
Completely open to guests, open-source and self hostable.
If someone is committed enough to help out but using Matrix (either directly from the web browser or installing the Element client) is too big a burden I'd question that original commitment.
PS: I'm not affiliated with Matrix in any way.
IMHO, Revolt is a better FOSS Discord alternative: https://revolt.chat/. Relatively young project, but they are unashamedly cloning the Discord user experience (even with the name). By default it uses infrastructure in Europe run by the project maintainers but can also be self hosted.