Have you actually tried deploying to webkitgtk ever?
Good luck "testing" your video conferencing app on webkitgtk - it doesn't support webrtc! It is still useful to test your error page I suppose.
Note that this is one example among many of missing features, bugs and/or horrible performance.
Here's a preview: no notifications, no :has, no TLA.
(Not blaming the epiphany devs for the situation here to be clear)
The thing is, Firefox/Gecko isn't embeddable (probably the one of worst tech blunders ever). I wonder if Tauri could wrap around Blink, instead? Then your app could just ask for Chrome to be installed.
The modern Qt web view component, QtWebEngine, is actually Chromium-based. So you could imagine a Tauri which uses Qt instead of GTK and uses QtWebEngine as its renderer instead of WebKitGTK.
Ahem https://github.com/tauri-apps/tauri/discussions/8426
That's a significant amount of workaround for something that "just works" elsewhere (and if I'm reading correctly doesn't work under Wayland).
It proves what everyone knows: that there's no reason WebRTC can't work in Tauri/Linux environments.
It also proves the point here: there are legitimate issues with the system-provided webview approach that are not always apparent.