Earlier quoted context omitted.
Wait, OnHub doesn't support IPv6?! That's inexcusable. There's no reason IPv6 couldn't "just work" too. Google Wifi had better support IPv6 at launch.
If you require IPv6 so crucially, you probably shouldn't be using consumer grade gear.
Since the OnHub only comes with Ethernet you'd have to put something between it and the wire anyways of course, but it then has to be more than a dumb modem, and you'd be forcing all traffic through the tunnel.
IPv6 isn't without problems, but many people use it without noticing, through consumer devices way cheaper than this. The ones complaining the most are the enthusiasts which suddenly can't reach their home server via IPv4 anymore.