[sabrex]

You answered your own question Google stopped really being open some time ago, and when they release new products, they don't tend to release APIs for them. They released an API for Picasa, and as you noted, it is depreciated and only some time before it disappears. Google never released an open API. There is an API behind the scenes, that the web site and phone apps use, but it is closed. Google doesn't obviously want people developing apps that utilize Google Photos. We are fortunate of the tie-in to Google Drive so that we can use the Google Drive APIs.

How do shared albums work? Do they also appear in your Google Drive, or only your own albums?

I wasn't aware that Google hadn't opened up the API for Google Photos. That's a shame. There's an article here pleading with Google to make the API openly available.

Albums in Google Photos simply allow you to create a new Album and quickly select what content belongs to that Album. You can optionally mark the album as a shared album and send the link to anyone. The option is available to let other Google Photos users add their own content to the same shared album.

Unfortunately, neither unshared nor shared albums will appear in Google Drive, but that's how my family and friends are sharing photos and videos with each other, since there is basically no need to re-upload the content anywhere. There is unlimited storage and the content is backed up anyway, so it's just a matter of creating an album and sharing the link and content from multiple people stays in one single place.

Here's hoping Google opens up the API at some point. In the meantime, the gdrive add-on is awesome for viewing the photos and videos in Kodi! Thanks again for your amazing work.