Stumbled upon this code:
private isSupportedLink(webview: WebviewEditorInput, link: URI): boolean {
if (MainThreadWebviews.standardSupportedLinkSchemes.has(link.scheme)) {
return true;
}
if (this._productService.urlProtocol === link.scheme) {
return true;
}
return !!webview.webview.contentOptions.enableCommandUris && link.scheme === 'command';
}
_productService.urlProtocol is not making a lot of sense when running from the Web UI, it is in fact set to be an empty string currently.