I "can" use the native Skype for biz client to make and receive calls, but its through and on prem SFB server. I do have a hybrid deployment for SFB, but I haven't figured out how to connect my IPO to the cloud SFB yet. Not sure if I'll even explore that route.
Also - MS is moving towards Teams which I'm slowing trying to learn how to connect IPO to that. Stay tuned.