What replaces ZeroTier or Hamachi when the provider blocks them?

This does the same job — it puts machines behind NAT on one local network — but over ordinary HTTPS on port 443. To the network outside it is a connection to a web site, not a VPN protocol, so there is nothing distinctive to detect and nothing to cut. No account in someone else's cloud, and no limit on the number of machines.

How do I reach a computer behind NAT without a public address?

Both machines connect outward to the server and meet there. No port forwarding, no static address and no router configuration — it works behind a mobile modem and behind carrier-grade NAT.

Is this the same as a remote-terminal tool?

It includes one — SSH from the browser to any Linux machine — but it is wider. Besides the console you get an actual local network: shared folders, network neighbourhood, printers, remote desktop and anything else that runs over Ethernet.

What do I need to run my own server?

The cheapest VPS with a domain name: one core and 512 MB of memory. The install script registers the service, configures nginx and obtains a Let's Encrypt certificate. The server is one file; the database is SQLite beside it.

Entirely — the client, the server and every feature. No subscription, no device ceiling, no paid edition.

Which systems are supported?

Windows 10 and 11 (64-bit) and Linux — Debian, Ubuntu and relatives — for amd64, arm64 and armhf. That covers ordinary computers as well as single-board machines.