We have very little MacOS expertise on the team (mostly Linux, server-side developers), therefore the question might not refer to everything about MacOS correctly, but hopefully close-enough base on Linux analogies to be understandable.
We have a WebRTC client application which works well in Chrome, on Linux and on Windows, with a WebRTC Gateway server to perform some customer support communication. We have got a query from a potential customer, who for some reason prefers to use Safari instead of Chrome, and wants to know if we could somehow offer an installable-executable .dmg file for MacOS, that renders the same functionality (i.e. WebRTC client application).
The installable-executable requirement is an appearance/perception thing, though for practical purposes, a URL and a valid/active account is enough to use the service.
Have you considered using Electron? Its based on a (slightly old) version of Chrome and may allow running your existing application with very little changes. https://bloggeek.me/webrtc-electron-implementations/ shows some examples of companies taking that approach.
Note that Safari has WebRTC support (lacking VP8) on High Sierra since last year.