Just tried the Android app. The automatically generated xkcd-style passphrase is really cool, but the app insists on storing it in the operating system's credential storage with seemingly no other option.

As it happens, I don't have credential storage enabled on the spare device I tested it on, so this was a bit annoying.

I've dabbled with several messaging apps from Signal to Telegram and a bunch of others in between, and in fact this is the first time that an app tried to make actual use of Android credential storage. I wonder what the advantage is, and how other security-conscious apps like Signal are doing without it.