IPv6 + transport mode IPsec + opportunistic encryption with TOFU or other topologies of trust (including WoT, DNSSEC and PKI). All that is standard, most of it

IPv6 + transport mode IPsec + opportunistic encryption with TOFU or other topologies of trust (including WoT, DNSSEC and PKI). All that is standard, most of it is available and only requires configuration (and, ideally, being turned on by default). There is very little use for companies like Tailscale in this setup, it’s scalable and works.