Ended up just paying for an IPv4 address to avoid the hassle.
I don't think this is "the year of IPv6" but it might be its decade.
Also IPv6 doesn't actually work reliably. You'll notice it when browsing the web for example, there are periods of 2-3 seconds without IPv6 connectivity. This does not happen on IPv4.
(Though I agree there should be no such distinction, in a real P2P internet)
As a Spectrum Business customer, I wish I could tell you whether or not that was true, but IPv6 isn't available to me at all. I'd happily (okay, not happily, but I'd be willing to do so) pay for an IPv6 block (I currently pay for five static IPv4 addresses -- one of which is eaten by Spectrum's required router, the other eaten by my own router, but that's a different discussion..Grrr!), but I can't even do that -- as it's not even on offer here (NYC).
It seems that there's wide disparity in how/where Spectrum implements its IPv6, so YMMV.