Here, the Ubuntu developers roll out in-house universe security patches (additional backports of new patches against historical versions of the packages), which was previously not available
I’m not sure every package should be considered supported in LTS, so this not being available by default looks ok for me
Huh, that was hidden deeper than I like. https://ubuntu.com/security/cves/about#security
https://help.ubuntu.com/community/Repositories/Ubuntu
https://askubuntu.com/questions/1452497/what-are-esm-apps-and-how-do-they-relate-to-ubuntu-pro
edit: adding some relevant links
From the link:
I’m not sure every package should be considered supported in LTS, so this not being available by default looks ok for me