Here are all the apps I found so far to extract my Twitter friends:

Twitodon finds your followers who also used Twitodon:
https://twitodon.com/

Debirdify scans your followers (or even muted lists!) for Mastodon addresses in their name, description etc etc
https://pruvisto.org/debirdify

Fedifinder searches your followers name, description, etc
https://fedifinder.glitch.me/

Direct link to @Randy_Au's #ML list:
https://docs.google.com/spreadsheets/d/1ihzEGJDi1h1WM13k3T3jlld0RpXoWQrhUw5ftkTS1SM/export

#TwitterMigration