Wow I hadn't even noticed that.
I started the video a long while back, and Peek was one of the first apps I recorded for before I shelved the project for a good while.
I see now on their Github the announcement, and last commit was 6 months ago.
It's possible that it will remain useful for a while though since it relies on major libraries.
When it does break hopefully someone will fork it and make the fixes necessary.

I'm working on a critical analysis of GNU/Linux, and backwards compatibility/breaking libraries/API's is one of the major points.
I'm still using Ubuntu 18.04, and I've found several AppImage programs that won't run because of my outdated GLIBC version.