Buying movies on Google Play ? Is that still a thing (or even was a thing at some point) ?
It's probably the best place to buy. The library is great, the prices are pretty cheap. You can buy stuff in SD and they'll often upgrade it to 4K, you can share your library with other people (5, I think) and best of all--your library is on YouTube!
Youtube is pretty much on every device so my library is on pretty much every device.