IPv6 - Is my device accessible from the internet?

Solution 1:

do not conflate routing, with firewalling. While NAT in ipv6 does exist, it's generally not needed. However just because a machine is routable (all the devices in the chain know how to get traffic to the destination) does not mean it is reachable (one of those devices could choose not to pass the traffic on).

So you need an ipv6 firewall, basically. If your home 'router' does this by default or not (i.e: it's actually a router/firewall device) we can't say without more information. You'd normally configure the v6 firewall the same way as the v4 one, - allow related and established traffic back in, and nothing else.