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 this is great! Wish I’d found it before I deleted my bird site accounts. I might fork and try to modify to take whatever the Twitter data dump provides for user follows or interactions.
@trisweb You will probably have to change the "friends/list" API request to "users/lookup" and provide the IDs in bags of 100.