Boot menu however still shows PureOS 2.1 – what did I miss?
That’s why it’s still alpha. 
We still need to work these details.
I expected to be able to boot into the new version, much like when I upgraded Ubuntu from 14.04 to 16.04…
I don’t understand, you booted successfully or not?
Anyway, if you come across a bug, we would appreciated very much to report it to our tracker: https://tracker.puri.sm/