That's a great utopian ideal (and one that I subscribe to), but there is no way that is happening outside really nerdy circles such as we probably inhabit.
It is of course possible to create signal clients that are forks of Signal.
I don't see how this is an -ethical- issue though providing the ethics of Signal align with that of the user (they do with mine), and if they're doing something unethical then you should not be using them anyway (hence me not using WA)
Trading one proprietary app that gives you ownership over your own data (WhatsApp) for another proprietary app that locks your data (Signal) is not an "ethical" replacement, it's merely a (worse) alternative.
With WhatsApp I can backup and restore my messages. With Signal I cannot. I had to reset my iPhone 2 weeks ago because "system storage" was magically taking up 30GB of my 128GB iPhone. The iCloud backup restored everything perfectly, including my 15-year old WhatsApp history. However all my Signal messages were lost. And even worse, this is apparently by design. You can't backup your messages on an iOS device. It's my data, let me do it what I want. But that's not possible, the data can only exist in a proprietary compiled app.
WhatsApp is a lot better in this regard. I can backup my messages in multiple ways, and I can even export a conversation as a ZIP file straight from my iPhone.
Which probably only exists because of network effects. My kids (18-25) don't use phones for phones, and rarely use email other than when they have to for work.
Completely agreed. I want to be able to talk to people from any modern reasonably-secure operating system. Specifically, I found that there was no possible way to use Signal on OpenBSD natively. The only [poor] workaround was to create a Linux VM and use the Signal app for Linux in there. Frankly, if a communication protocol isn't usable on BSD it's not acceptable to me.
Options like Matrix or XMPP give users more freedom