Did you mean the "Notice Log" within the web dashboard from Opalstack? I found there a password, but it wont work.
I used the SSH user to login with e.g. putty.exe change the path to the gitea application and use the follow command at the command line:
./gitea admin user change-password -u <username> -p <password>
I think if you change the SSH user's password inside the dashboard, in gitea the password isn't change. But I could also don't use the old password from the "Notice Log". Anywhere, with the gitea command it works.