We would not recommend Matrix for security considering the recently admitted their old encryption code was bad and a lot of clients are still using their old encryption code:
https://soatok.blog/2024/08/14/security-issues-in-matrixs-olm-library/
oftheair
joined 3 months ago
Yes, we think we should pay but in the sense that we should put more money into non venture capitalist and non shareholder backed, non-commercial, open source and privacy-focused sites and services etc, and forgo the commercial sites and services that think they need to erode our privacy in the first place.
Lilo & Stitch, 2002 disney movie
The only thing that fits most of your needs is Signal, we have looked into this heavily and nothing has as many features, is as easy to use as and has a strong of focus on privacy and security as Signal, so it's either that or Whatsapp.
You can techically use signal on multiple devices, by linking them instead of setting them up as each their own 'host', if you want it on multiple phones or multiple android devices you'll likely have to use Molly, I believe this would work, but am unsure.
Matrix should not be considered because of this:
https://soatok.blog/2024/08/14/security-issues-in-matrixs-olm-library/
and Threema is pretty bad historically ( https://soatok.blog/2021/11/05/threema-three-strikes-youre-out/ ), even though they have improved in the last year or two, but their desktop offering is pretty awful, as unless you want to use the beta and use iOS then you have to keep your device attached to the network, on and open on Threema only.
Signal really is the only option here.