Hi, after testing one by one each feature of Quark, just to find wich one was the one that prevented undergarden dimension to work, i find that it was the 'realistic' feature. When enabled, undergarden dimension doesn't get registered, but when disabled, it does.

I can't pastebin the log, it's too big it says, but if needed i could do something, just ask!

Already talked with Quek, The Undergarden autor, and thinks that this is a forge thing, but i submit this here just in case.
Thanks!

Hello! Quark's moved to 1.18 now-- unfortunately, this means that (unless your bug is critical and/or game-breaking), we're closing support for issues filed for versions prior to it (e.g. Quark on 1.16).

If your issue still occurs on 1.18, or if your issue happens to be rather critical (e.g. consistently crashing the game with no other mods present), please leave another note or open a new issue. Thanks for your cooperation!

You can fix this by generating your world with realistic preset, then remove the settings in your server.properties your world will keep the generation as realistic but the rest of the dims will be able to generate.
Restart your server once again and you'll be able to join the other dimensions.