The Android Client (3.10.1) deletes the local files after the upload to the server.
Example -> Select picture -> share with -> Nextcloud Client -> upload.
Local File is deleted.
Client: Samsung Galaxy S10+ With Android 10, NextCloud App 3.10.1
I’m also suffering from that problem: I want to upload (copy!) a file, e.g. a picture but it gets deleted after upload. I could not find an option anywhere to change that.