IPv6 address, as a sentence you can remember

Outside the home, in other words in networks other than at home. Potentially without VPNs. Accessible from other public IP addresses, potentially limited scopes of those.

It seems you're thinking that allowing the traffic from other public networks is an all or nothing thing. That either you allow all public network traffic or none of it. That's just not true. If I know my office network is one prefix, and I know my friend's house is another prefix, and I know my cellular carrier in my city is usually this prefix, I can greatly limit the scope of access. It doesn't have to be an all or nothing, either its open to every single other device or only local devices, I can define exactly which networks or devices I want to allow the traffic from or not.

If I wanted to just let my friend's network audio receiver to connect to my music server, I can add it's public ip address and allow that traffic. No VPNs, no tunnels, no proxies, no non-standard port assignments, just directly allowing it to talk to the music server. All through the public internet, but still locking down my music server to just local traffic and his remote network audio receiver.

That's all still "public" networking.

> In most parts of the world, I think, IP changes every time you restart the router, even IPv6.

Often not with IPv6, prefixes stay pretty consistent usually. Not always true, but often true. I've had the same prefix for many, many years at multiple locations and multiple providers without having any kind of payment for static IP addresses.

> So let it. Forward your own chosen port to 443 of the machine with the service.

So now I have to remember the port for local and the port for remote along with different IP addresses for both, or I can just use the normal service port and the same IP address either way, and have one DNS entry for that IP address and it works anywhere I want it to.

> But let me know how much you like it after your first cryptolocker.

Entirely a tangential, unrelated point once you understand how things like "firewalls" actually work.

> I suppose your backup storage is also public on the internet

My most important backups are offline and offsite. But for other stuff, yes, it has a publicly routable IP address. Its not generally accessible publicly though. There are these things called "firewalls", they're really quite neat. One should also think about authn/authz as well next time you're working on your storage solutions as well, it'll do a lot to prevent cryptolocker issues you're so worried about.

For instance, AWS S3 is all technically accessible publicly. Its locked down by policies, not by NAT limitations. And yet its generally seen as a very secure place to store things, assuming one has the right policies in place. It doesn't take it being behind a NAT to be secure, because if that's the major part of your security posture preventing your stuff from getting cryptolocker'd you're doing things very, very wrong.

> I use bookmarks

Ok, and you hop on someone else's computer and...where are my bookmarks? Oops! Or I want to connect back to my media server from a friend's streaming device...where are my bookmarks? Oops!

And once again I bring up things like game consoles and other P2P applications which just work far better with actual publicly routable IP addresses directly. Strict NAT configurations will often cripple these services and good luck trying to have multiple consoles operating at once. CGNAT makes online gaming for some of these consoles just completely unusable, but if we just supported IPv6 it would have no problems.