When I try to start akonadi it crashes immediately. And so does Korganizer btw. Strange thing is that they both are ok when running inside Kontact. I installed akonadi in the running live-distribution (neon user 14-06-2018) and it also crashes at startup. I tried this on another computer (eight years younger/also intel based) with the same result: akregator crashes when it starts.
if you run them from terminal do you get any extra output?
I am a lontime kde user and I use Neon from its beginning. But from time to time I re-install. I did exactly that with the build from 14 june. But I discovered that I installed the dev-unstatable branch. I don't know if that was due to a mistake of mine or something else. Anyway I downloaded the build of 21 june and installed it and I am very happy to say that things look much better now. E.g. akregator and korganizer function 100%