Lora-Chat-Device VS Kontalk

> then try to find your contacts again (which may be cached by your client or not)

You can save XMPP account IDs in any mobile address book.

> Finally, you have to convince "someone" that this is just you with another account on another server. There is also no verified E2EE anymore.

I'd pretty much just do a video call at that point.

> How is this different from "when Signal goes down one uses a completely different instant messaging system", apart from using another client?

You don't have to use another client software.

> Which means: If one of these hosting companies blocks XMPP traffic (e.g., if a rogue state starts censoring) or one of these XMPP servers goes down, a huge part of XMPP users is affected.

Equally applies to most messaging apps out there. Some XMPP apps have the benefit of also supporting using Tor and hidden services - Signal/WhatsApp/etc, don't.

Don't want to use the Internet at all? You can even go wild and do something like: https://github.com/ddamianus/Lora-Chat-Device - I realize this is something most people would not do, but XMPP's _flexibility_ allows this to be an option if it was something people wanted. Can't do Signal over LoRa.

Yes, Quicky from the Conversations developer who bragged about copying main features of WhatsApp and Signal.

Another one is Kontalk, https://www.kontalk.org/.

Both XMPP clients require a phone number, and both present the phone number as a benefit in comparison with other XMPP clients without this requirement.

It doesn't support OMEMO (the Signal-based end-to-end encryption protocol used by most XMPP apps today) (kontalk/androidclient#132)