2.1.28 not in the archive & syncing between different versions

Why no 2.1.28?

2.1.15 is the newest version I can run with my main computer’s Linux distro. I want to try a newer version on a second computer. Which versions can sync with 2.1.15?

It is available: Release 2.1.28 · ankitects/anki · GitHub

All 2.1.x versions can sync with each other.