Has anybody tried to install Wireguard?

The error you’re seeing is very similar to the one in this post: Mantistek WA150 - #7 by skdauser, which I can reproduce.

The Mantistek WA150 code does not produce the error on Raspbian Jessie or Debian stretch (amd64) (I’ll look at Raspbian stretch when I have a bit more time).

So far, it looks like there might be a problem with the OSMC headers package.

Update: The problem does not occur with Raspbian stretch.