Exactly. You can't self-host Signal, also it requires a (proprietary) phone number, which you don't own.

The article fails to mention the multitude of platform providers that make self-hosting easy - such as Start 9, Casa OS, Umbrel, or Cloudron.

With these you can deploy your own simplex server, matrix instance, or nostr relay.

The UX of Simplex has improved significantly in the last 12 months, and they are now working on solving the "large group" issue.