Uploading to both services is still supported through the Backup and Sync app. But once uploaded they are independent copies and deleting from one doesn't delete from the other. I also expect that this support will be deprecated at some point in the future.
Not keeping Drive and Photos in sync really killed it for me. I ended up switching from Google Drive to Dropbox but I still use Google Photos.
I have photos added to my library in Dropbox automatically added to my Google Photos library and this has worked well so far. [1]
[1] https://github.com/jmathai/elodie/tree/75e65901a94e14e6fd1ff...