Have a look at how inputstream.adaptive depends upon widevine CDM files being installed to the OS in a known location. If the files are not present, the add-on initiates a download of a ChromeOS update file which contains them, and then the update file is unpacked and the needed files are moved to a consistent location where inputstream.adaptive can find them. This keeps the core add-on size small (and avoids the legal issues involved with pre-bundling the widevine files).
In your case you can detect distro by looking in /etc/os-release and if LE, initiate a download of the needed (bulky) files to a cache location under /storage/.kodi or somewhere else on /storage, and if not LE, check for the package being installed in the known location. Then set the media file paths to either the cache location or the /usr location as needed. On other distros you'll need to gracefully handle the dependency on the app binaries being installed anyway.