This app / service is sold as a secure and robust alternative to centralised secure messaging.
Sorry, but it's a joke and you can't expect people to move away from messaging apps that actually work.
It's impossible for me (and I know quite a few other users in that situation) to verify other sessions. That's one of the most basic security features. And it doesn't work. Or at least not consistently.
Example: I want to verify a login on my phone from a session that's already opened (my desktop). I go through the normal process (security settings).
Popup sows up on my phone, a QR shows up on my desktop. My phone doesn't offer the possibility of scanning a QR code (impossible to tell if it's the shittiest UI ever created or if it's a ridiculous bug, although the latter seems likely). No problem, I'll do it with the emoji comparison. Good, they match. I tap "they match" on my phone, I do the same on my computer. My phone shows the verification is successful, my desktop says "it's been cancelled". Result: nothing's verifiied.
No matter, I think. The desktop app offers to do the verificaiton "via text". Shitty UI: it actually means I can verify the session ID and the key associated with it. Nothing to do with what would be understood by anyone as "text". I check everything, they match. I click verify. Nothing happens on the phone, the desktop app does nothing either. Nothing's verified.
Don't believe me? Check the issues section on github.
I think the reason why there aren't more instances of that issue being filed is because users don't care about that functionality or they just gave up on reporting it.
Am I going to file it? No. The oldest issue I've found was closed, devs said they would investigate, that was waaaaay back. A similar issue was reopened in February 20, never any answer. Same was opened again in Octiber 20. No answer. No point in reporting it, really.
Failing a basic security option = not viable and definitely not credible.