(not at home so I can't also try to replicate this on my Manjaro desktop)
After pressing the button to create a forum account (once all personal info and account creation fields were filled in) I would repeatedly land on a page with the following text: "We cannot detect if your account was created, please ensure you have cookies enabled."
Cookies are definitely enabled.
I was able to finally create the account from Safari and then log in successfully in chrome.
Maybe I'm doing something wrong, but I thought I'd post this in case it isn't me (and in case others are running into the same issue).
Thanks for making and maintaining my favorite OS!