Just wanted to close the loop on this.

I am not sure at which point exactly things go wrong, but the cause is apparently a bug in the installation routine of the plugins CMake script.

I was able to get my project to link with the release build of the plugin by uninstalling everything, and then installing only the the release build. The downside to this is, that now for both build configurations (release and debug), my project will only link to release. This is good enough for me for the moment.

Many thanks again to @Tsyvarev for helping me to debug this. I was not able to fix the plugins behavior through any of the CMake settings mentioned, unfortunately.