Might be a good idea to wait some time to see if the API changes. It is not documented yet as it is very recent so things could change.

https://developer.riotgames.com/docs/lol#game-client-api

I am not wishing for "professional" upgrade/downgrade handling, but can there be something?

I am getting this (#1609 (comment))

and then also that:

The first popup is normal (though i'm noticing now that it says overwatch, which is obviously a mistake)
After this, i'm not sure what causes it to continue erroring out. This should happen once when you update, and no more. Does this happen more than once on your system?

The first popup is normal (though i'm noticing now that it says overwatch, which is obviously a mistake)

I didn't take a screenshot, as I was not planning to report this. I recycled the one I used for Overwatch.

At least, this time, both popups were only shown once! 😃

Good thinking me, that I didn't open a new issue 👍