tawk.com is a free and private, non-intrusive, WebRTC-based solution you might like very well. You can reserve your own room or create one at random. The technology behind it relies on desktop browsers such as Firefox or Chrome and sets up a peer-to-peer connection between the chat-ees (if that's a word). In any case, it also works on late versions of Android.
You can even get notifications when someone attempts to join your room while you're not in it. You can do audio/video/file-transfers. They provide a simple copy/paste code-snippet for inserting a sort of call-metawk.com button into any interface. You can likely even get your own url - mine is tawk.com/mikeserv for instance. It's pretty handy and completely browser based.