Even if your ipv6 host or border firewall allows pings through, it's not practical to scan an entire /64. There's just too many addresses in it, and your devices will frequently change them.
> I don't want anyone to know which one I'm using to access their website, I don't want anyone to try guess the OS and version of my devices, etc.
They already do this through fingerprinting that operates with higher-layer protocols.
> And now I'm scared to have a simple DLNA media server because I can't just install WireGuard on the TV.
This is very simple to implement. Ensure it's listening on the link-local address. That's the IP that starts with fe80. These are unrouteable by spec.
It's very hard to distinguish my iPhone and Mac from the other dozens/hundreds people have in my building just through fingerprinting. Very easy if they have separate IP addresses.
Ad link local - cool, I'll look into that, thanks.
It doesn't matter if everyone in your building has an iPhone and a Mac as well -- there are things about virtually every single one of them that make them unique.