What is Homeland? I explicitly disable IPv6 because I don't trust the firewall, specially on an auto-updating device.
It could be with UPnP, which as a security conscious person you likely have disabled. Do you trust it staying disabled or none of your many devices trying to use it to poke holes in the NAT?
Even if you have to use your ISPs modem/router device, it might have a bridge mode where it just becomes a modem, enabling you to use your own router. It might be worth checking this option if you didn't already.
If you don't trust the ISP device to firewall, then you can't trust it even for v4. You need to run your own router.