Maybe I am being too simplistic here. But I have never received a spam message to my XMPP account and I don't know how a spammer would find it.

In a phone-based system a spammer can spam a list of numbers, or use contact lists that are easily shared via phone permissions. There are several low-effort discovery processes.

For e-mail, you get spam when you you input your personal e-mail into forms, websites, or post it publicly.

But for something like XMPP... It seems rather difficult to discover accounts effectively to spam them. And, if it is an actual problem, why not implement some kind of 'identity swap' that automatically transmits a new identity to approved contacts? A chat username does not need to be as static as an e-mail or a phone number for most people.

I just don't see 'spam' as such a difficult challenge in this context, and not enough in my view to balance out requesting a phone number. Perhaps a spammer can chip-in?

SimpleX is coming nicely along. Should be good to switch next year once they got their desktop apps polished up

Privacy is not necessarily anonymity. Signal uses a phone number to prevent spam and DDOS attacks on their network. Session doesn't do this and got wrecked by DDOS attacks to the point where most of the major groups are pretty much dead.

Use Signal to talk to people you know. That's what it's for. You don't use it for anonymous chats.

Is there a quick explanation of what signal actually does? I don't understand the need for a phone number either. Jami doesn't ask for a phone number. It has other deficiencies that make me not want to use it, but those are technical rather than policy, more or less. Similarly, irc (I'm luddite enough to still be using it) doesn't ask for a phone number either. So this is all suspicious. There are a bunch of other things like this too (Element, Matrix, etc.) that I haven't looked into and tbh I don't understand why they exist.

Jami.net

Ignore the comment saying signal is "end to end encrypted" "private" etc They are simply stuck in a delusional state where they try to convince themselves that signal is the best option so they can continue using it. Nothing is private if it isn't fully libre because you never know what the proprietary code is doing. The signal protocol itself has its source code released, and the encryption and security code is publicly available, but the signal Foundation has stated that it uses both free code and proprietary code. Their reason is UI, but it's hard to make sure whatever proprietary code is being used for because you simply can't see it. As GNU puts it: "You're walking in a pitch black cave". Jami is fully libre and is a GNU project. You don't even need any phone number!