Thanks for the info. I was under the impression that you were claiming that Matrix is less secure than WhatsApp. If they both leak metadata then they're roughly equal from a privacy perspective no? I guess with WhatsApp you can't know the extent of metadata leakage, but at least with Matrix, you have the advantage of knowing precisely what data is leaked.

Not trying to push Matrix or anything, i've been using Signal for some time already anyway, but thought i'd see what alternatives there are. The lack of chat backups is a real drawback, though since the Android version has a backup option, i'm hoping it's something they'll eventually implement?