Just to circle back here in case anyone else has been watching this - VIVE Browser is now supported on the Focus 3, at least on my headset on the "Beta" branch. The performance feels about the same as the old Firefox Reality for now, but hey I'll take it...baby steps toward a fully supported, WebXR compliant browser with enhancements for VIVE products is fine by me as long as it's getting updated regularly. I do hope the team considers making it an open source project on GitHub so people can more directly contribute and follow its development.