OK thanks for the explanation. But it now produces a slightly different error for the minimal example from the beginning ot this thread (the 2.6.0 is green and the 2.9.1 red now)
$ mix deps.unlock cowlib
$ mix deps.get
Resolving Hex dependencies...
Failed to use "cowlib" (version 2.6.0) because
cowboy (version 2.8.0) requires ~> 2.9.1
gun (version 1.3.2) requires ~> 2.6.0
** (Mix) Hex dependency resolution failed, change the version requirements of your dependencies or unlock them (by using mix deps.update or mix deps.unlock). If you are unable to resolve the conflicts you can try overriding with {:dependency, "~> 1.0", override: true}
Does it have to do something with Mix phx.new deps error - cowlib - the dependency does not match the requirement ?
