Onlyif seems to not be used correctly. As I have understood it should either specify a command or a module, not be fed a dictionary raw from pillar. I get the following warning when executing with a custom repo:
[WARNING ] no `fun` argument in onlyif: OrderedDict([('comments', ['installed by salt']), ('enabled', 1), ('gpgcheck', 1), ('name', 'deb [arch=amd64] http://mirror.example.com/download.docker.com/linux/debian buster stable'), ('file', '/etc/apt/sources.list.d/docker.list'), ('key_url', 'http://mirror.example.com/keys/docker.gpg.key')])
https://github.com/saltstack-formulas/docker-formula/blob/master/docker/software/package/repo/install.sls has a couple of issues:
Pillar: