If you more or less agree with what I say here, is clear that one of the approaches for connecting several cloud and on-premises eco-systems is by means of an iPaaS or integration hub (iHub).
As an analogy, think about how you connect different physical systems by means of a communication stack (router, switch, …). The same way, an iPaaS is a virtual hub where you plug/unplug your subsystems as they appear/disappear in your complete IT stack.
Enjoy 😉
approaching off the bow 