As someone else said, this bug was fixed in the last versions (>1.0). However, I, personally, had problems with the 2FA code field not showing up because I was using the autofill from my password manager (1Password). Took a bit of experimenting to figure this out, but I just copied and pasted my username & password instead, and then everything worked normally. Just putting this here for whoever else might look at this post next with the same problem.

Also had another problem where my 2FA code was being generated with SHA1 instead of SHA256 as Lemmy uses, but that's probably because I set up 2FA way back, and it most likely wasn't specified properly.