The desktop-client download link for 16.04 at https://software.opensuse.org/download/package?project=isv:ownCloud:desktop&package=owncloud-client is broken.
If I try to download owncloud-client via apt-get, it fails to verify, even after adding the keys.
If I download the tar.bz or zip file from https://owncloud.org/install/#edition and then try to verify it against the gpg key on that same page, the verification fails.