Hmm this is new to me. I was always under the impression that traffic between Qubes only uses IPv4 (probably because internal addresses are IPv4). So you’re saying that if I want to block IPv6 internet traffic, I should do so by configuring sys-net and, if I’m using VPNs, the relevant firewalls?
By the way I disable IPv6 via qvm-features [VMname] ipv6 '' for all VMs, but this doesn’t seem to be the cause of the inconsistent network connectivity I experienced for my torrenting VM that I posted about recently. I’ll take a look at it.