Comment # 6 on bug 4286 from Nicolas Chauvet

(In reply to Vasiliy Glazov from comment #5)
...
> 3. Path:
> /usr/lib64/chromium-browser/PepperFlash/ for x86_64
> /usr/lib/chromium-browser/PepperFlash/ for i686
> As these paths are in Fedora chromium package.
> 
> For widevinecdm:
> /usr/lib64/chromium-browser/ for x86_64
> /usr/lib/chromium-browser/ for i686

You have to use a mechanism and install the binaries in an agnostic directory
similar to adobe (npapi)flash-plugin (such as _libdir/pepper-flash-plugin).
Then use trigger post to create a symlink on purpose once chromium /
QtWebEngine / other package installation.