I wrote a nano tool that tries to extract the #Fediverse accounts of your #Twitter followings: https://fedifinder.glitch.me/

It searches for the patterns @[email protected], [email protected] and host.tld/@user in the screen name, description, location and URL field. It displays them to you in the correct format for easy copying as well as a CSV download that can be imported to #Mastodon.

New version: https://fedifinder-backup.glitch.me/

Fedifinder

Fediverse accounts of your X/Twitter followings

@Luca neat tool. Thanks for that! Might it work against lists created in Twitter?
@vbatts It would need some bigger changes, so I don't know if I will get to implement them. But it's the third point on my current to do list (1. check if instance is alive 2. search for tweets by followings that could link to accounts).