If I get 1400+ requests to my website from Mastodon servers (to validate the link in my profile), and only 4 of them speak TLS 1.2 instead of TLS 1.3, I can be reasonably sure that those servers run OpenSSL 1.1.0. Or even older.

I have no idea how accessible the documentation for maintaining a Mastodon server is, but I feel that there should be instructions there about not using versions of critical components that are over 6 years old.