Why do people have Mastodon names in their Twitter profiles? Because https://fedifinder.glitch.me exists:
1. Open the link & log in. (No, they won't learn your credentials.)
2. If people you follow have their Mastodon handles in their profiles, this will give you a list of those. (Which includes email addresses, sadly.)
3. You can even download a CSV and import it here in Mastodon. (I haven't tried that, because I only had half a dozen handled listed.)

#TwitterMigration

Thanks to @luca!

In case you've already tried it: It's well worth it to run @Luca's fedifinder again: https://fedifinder.glitch.me

For me, the number of hits has tripled within the 2 day since I did this last.

Fedifinder

Fediverse accounts of your X/Twitter followings

@Luca @sbi I assume this only works if you still have an active Twitter account.
@rainynight65 @Luca Since it searches through the accounts you follow, yes.