I've worked as a software developer for 8 years so far. I have yet to meet a single fellow developer who is privacy-conscious.
I'd love to use signal, but it'd be a very silent place, and have to have WhatsApp anyway. So, instead of trying to entice others, I just try to win a one small battle at a time, reducing my cross-section step by step, where I can.
Until laws are implemented that forbid this and/or security improves to do so, it doesn't matter how good the encryption is if it's running on a fundamentally insecure device.
Being open source is nice, but not required for privacy.
https://www.cnbc.com/2021/09/02/whatsapp-has-been-fined-267-...