I actually did this when you helped me set it up in this thread (lots of gratitude for that by the way):
No joy.
I have been meaning to update that thread with the UCI script used and click your Github answer as the solution, but the forum has been giving me issues.
Which is what I've noticed. Websites with an IPv6 address like this forum or YT seem to have intermittent problems loading. Probably not related since those go out over the VPN. My VPN over WireGuard is fast enough to live-stream even when congested, so there's no reason for YT to auto-switch down to 360p unless it's getting timeouts in the background. But like I said, probably unrelated.