There seems to be a gross misunderstanding of how everything works here. Any platform will need to provide data to authorities when “asked properly” - as in, receives an actual order from some enforcing body that has authority on the subject in question. No commercial company will fight the CIA in court to protect your data. The best you can hope for is that they minimize what kind of data they collect about you in the first place - in the case of E2EE, they will only have access to IPs and other metadata such as connection timestamps and nothing else. But all of the services you listed will collect at least IPs and most will do phone numbers as well. The only difference with Telegram is that they’re transparent about it. You can either avoid using commercial platforms altogether, or use them in a way such that data retrieved from them will be useless. But believing that “Signal will never give my IP to law enforcement” is delusional.

Indeed… IPv6 needs to be actively disabled, not enabled, by default.

Can’t you hide bot accounts from your settings?

Unless your ISP provides IPv6 connectivity, which gives every endpoint a globally-routable address. Firewalling at the router only works because of NAT.

Sounds horrible

You might be interested in CyclOSM to plan your routes

I can’t change my router’s DNS

Do you mean you can’t change the DNS server in the DHCP settings or the server the router itself uses? In the first case you might be able to use Pi-Hole’s DHCP server instead, while for the latter it shouldn’t be an issue - I actually usually leave upstream servers configured there to avoid loops. BTW, you might also be able to flash OpenWRT to your router

A computer that is used by a user, aka “not a server”

Not true, SSH keys need their passphrase to be used. If you don’t set one, that’s on you.

Probably not worth trying to actually use today. I’d leave it as it is, imo it’s better as a small piece of history - Android on PC is pretty niche