Perhaps not much, but last year I was looking at using IMAP as an export/import path for a relative's old Eudora mails to some much-more-recent client. I insisted on it, after I found out it could no longer make a secure connection to their e-mail server.

That said, I was saved/pleased by Eudora2Unix [0], one of those projects that represents a very long slow burn of successive people with a similar niche struggle. You might think Thunderbird would have an import tool for that, but it's been so many years it didn't survive...

[0] https://github.com/jonabbey/eudora2unix

I'm working on one this week, from a cPanel-hosted email to Google Workspace. There are probably still quite a number this category will still be happening.

Then there's all the people who want to exit Big Tech or US-based companies right now.