[Dagonfly]

Most hosts will generate both a stable and a temporary address when using SLAAC. The temporary address will be used for outbound traffic but the stable address will accept incoming traffic.

So there usually is a stable ULA or link-local that you can put in a local DNS AAAA record.

The PITA is that many services prefer GUA over ULA if available and don't gradually fall back to ULA if the WAN goes down. And you will still need dynDNS to VPN into your network because ISPs are allergic to stable IPv6 prefixes.