About this question
The router that my ISP has delivered contains an IPv6 firewall. The only configuration option is whether it is on or off. Apparently, this firewall simply denies all incoming connections.
I understand this is to prevent exposing all hosts and all their open ports to the entire internet.
If I want to receive incoming IPv6 connections then I will need to disable this firewall.
Is it dangerous to disable it? I wonder if devices such as PCs and mobile devices are secure enough to be exposed to the internet. They certainly are supposed to be secure but are they secure in a practical sense?