If you try to create an account and it does not work - no error message, no timeout, just starring at a spinning wheel forever -, look at your chosen username. If it is longer than 20 characters, try a shorter name.
After you have gotten through the process of account creation, you might think to yourself, yo, but I can totally choose a display name, right? If you go to your account settings and change your display name and find yourself again, without an error message or anything, starring at a spinning wheel forever - try a shorter display name.
I have been told that the standard for usernames is 3 to 20 characters, though this can vary from instance to instance. But Lemmy does not tell you that. Which can be very confusing.
Disclaimer: I post this as a “for your information”, not a support request. I don’t know if the admins of this instance would even be able to help here. This is a Lemmy problem, not a Blahaj problem.
Unicode characters seem to be a problem as well, I had Esperanto letters in my display name and Lemmy wouldn’t let me post (comments were ok tho?), I tried removing them and now it works.