I'm not entirely sure that I'm following, because my upload flow from Google Photos puts me into the "Select photos" mode where I can tap multiple photos to sel

I'm not entirely sure that I'm following, because my upload flow from Google Photos puts me into the "Select photos" mode where I can tap multiple photos to select them. I'm assuming that you're been sent to a photo picker screen and can only choose one at a time. Have you tried holding a tap to enter multi-select mode?