Videoportal PWA (Progressive Web App) Video offline function?
Yes, you can use the Cache Storage API along with service workers to handle offline video playback.
There's a complete sample app at https://github.com/googlearchive/sample-media-pwa.
If you were to use the Workbox libraries for handling your caching logic, then this guidance should help. If you don't end up using Workbox, then you'll need to implement some logic to handle Range: requests in your service worker, or else your video playback will likely not behave as expected when the <video> element tries to load a partial chunk of video bytes.