Immich has breaking changes too often, so I disabled auto updates for the server and phone app. Updating every few months with backup beforehand is a good tradeoff for something as important as images.
Reading patch notes is especially important with some Immich releases requiring minor admin intervention, e.g. running an extract metadata job.
The global IPv6 address is usually not directly reachable from the internet for incoming traffic. There’s still the router with a firewall which blocks all incoming connections, so having an IP for each device doesn’t make a difference for security.
With IPv6 ports still have to be forwarded on consumer routers by default, the main difference is that it doesn’t have to be translated to a different IP.
This also means I can have multiple hosts on my home network listening on the same ports, because their public IP’s are different.