Thanks for the feedback. The username and password are indeed correct. I copied and pasted from Bitwarden and used the exact same ones to login to the lemmy.ml site. I do wonder if there is some sort of anti-bot measures that Colonel Sanders mentioned below.
Also: I tried just my username vs email but neither worked and I also don't have MFA enabled yet. Super weird.
EDIT: opened an issue on Github: https://github.com/CMahaff/lasim/issues/4
Thanks for this! Just gave this a try, downloaded from .world just fine, but uploading to .ml gives this error: ERROR: Failed Login - HTTP status client error (403 Forbidden) for url (https://lemmy.ml/api/v3/user/login)