Or as use case for a NIP 04 messager app on Nostr. #android
Then you share your media as blob to relays? That's a nice extension, nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z - also could share into my kind 1 timeline.
Discussion
Both "post" and "DM" should be an option, yes. And whatever the user has set should be used. For me it would default to a nostr.build upload.