I don’t think that the Android app is quite “there” yet. For example, Ello does not appear in the Android Share menu. I have a ton of my artwork on Google Drive. I should NOT have to download art to my phone in order to upload it to Ello. This functionality is ridiculously common in Android and should not require much to implement.
I submitted this as a feature request and received the following reply: “The concept has come up a bunch of times. I’m not sure where we’re at on making it a reality, but hearing it again is always more motivation to make it a priority. Consider your request duly noted.”