How secure something is an spectrum. Sure self hosted matrix is a lot safer than sending your messages through meta servers for example. It’s about what is the threat levels of what one is doing. Total tinfoiling like writing your own quantum proof multi encryption ciphers and sending that over an tamper proof usb stick with self destruct mechanism by a carrier pridgeon is not necessary or practical for average people who just want privacy, but for critical government applications and especially the military it might be. That is what we are talking about here.

It’s not, unless they’re some sort of cryptography expert with a peer-reviewed white paper pending publication. The Signal protocol (GPLv3) is extremely robust and has almost no capacity for metadata generation, and both the app and server-side code are under the AGPLv3 (technically if they were compromised they could use different, unaudited server-side code, but refer back to “basically no metadata”). Signal has essentially no capacity to be compromised; they can’t even bait and switch users with a pre-compiled app whose source code isn’t the publicly available one and actually has a backdoor because their builds are reproducible and it would be caught immediately.

Maybe they take issue with the crypto bullshit, which is valid but doesn’t compromise messaging security. Maybe they don’t like that they took away SMS, which I completely agree with, but also actually makes it marginally more secure. Either way, I seriously doubt if they had any mathematical insight into Signal being “compromised” that they would be here hanging around on Lemmy right now.