After finally fixing my installation of OSMC and getting it to update again, I noticed that steamlink was gone for me.

After installing it again:

I noticed that it would like to uninstall OSMC to install some EGL dependencies.
After playing around for a while, I found the two issues which prevented steamlink from detecting that these dependencies were already provided and using the osmc libraries.

I put these changes into patches listed in this gist[gist.github.com].

Maybe these (or similar changes) could also help keep steam link compatible with OSMC in general.