It doesn’t seem like there is any documentation on this from what I can find. With that said it seems the easiest way would probably be to just setup SMTP by following the official documentation.
If that’s not an option you could edit the user table within the database.sqlite file. If you’re using docker this will be located in the .n8n directory where you started the container.
If you’re not familiar with interacting with databases, you can use a free GUI program like https://sqlitebrowser.org/
Using this tool you can visit the “Browse Data” tab and select user from the “Table” drop-down.
Replace the contents of the existing password with the following.
$2y$10$/LDSRRyy6JeJhArBvbO3COudgZWx2ug9tsl2L3x5Vf6PXfgxM8DmC
Click Apply and click the “Write Changes” button at the top.
You should now be able to login with your previous email address and the password admin