If you want to collect tags in GTM all you need to do is enable advanced embed code when publishing your videos. This will include the spotlightr.js SDK in your embed which will communicate with your GTM instance.
By default, we are firing the following events:
spotlightr-video-loaded
spotlightr-video-played
spotlightr-video-paused
spotlightr-video-ended
If you require additional events, just let us know.