I used a website, (the USCIS), which pointed out that they accepted emojis in the password.
Edit: remembered which site it was. It's mentioned here, although they may have switched to id.me now, so the rules may have changed.
https://www.aila.org/aila-files/83E22577-0F60-4BBA-AF2B-4AECC7F28F5E/23021709.pdf