This may help: Yahoo requires a different password when using an email client and requires OAUTH2 authentication. This URL may assist: https://help.yahoo.com/kb/SLN15241.html

There are no app passwords with OAuth2 authentication, you'll have to use the main account password.

What error message do you get?

Also, please post your Troubleshooting Information. At the top right of the Thunderbird window, click the menu button ≡, then select Help > More Troubleshooting Information. Press the "Copy text to clipboard button" and paste the information into your reply.