As a reward for installing ESM/Ubuntu Pro, that version of ffmpeg will break vlc: https://bugs.launchpad.net/ubuntu/+source/ffmpeg/+bug/204274...

Manually upgrading the source .deb to the (ABI compatible) ffmpeg 4.4.4 and compiling gets all the security fixes and seems to work. It looks like backporting just the security fixes was done incorrectly in Ubuntu's ESM release.

My main concern with ESM/Ubuntu Pro is that patches don't get as much community scrutiny and help as other updates. In this case it's broken a fairly major piece of software on what's supposed to be a super-stable LTS release.