It's announced here as also being in beta for public repos: https://github.blog/changelog/2021-06-23-issues-forms-beta-f...
1,350 karma · joined May 31, 2013
Because of this my personal webserver, running nginx on Ubuntu 18.04, started offering TLS 1.3 without any manual action on my part, because the server is configured to auto-apply updates from these repositories.
I'm not entirely sure, but I think HPKP could have prevented this for returning customers, because Fox-IT would have been able to pin the key of their own certificate. Then the new certificate used by the attacker would have been rejected by the customer's browser.
(Settings → General & Preferences → Theme → Dark)