In v2.10.6 (pre-release) this looks fixed i.e. clicking on "Enable encryption" does trigger encryption actions.
How to encrypt, setup of Master keys, etc. is out of scope here, so for me this issue has been solved.
(Also, v2.10.6 looks better-behaved in terms of batch encrypting data than v2.9, so it's possible there have been other improvements related to encryption.)