@switchingsocial@mastodon.at Wheter is "secure" completely depends on once threatmodel, i wrote an article on that:
https://write.privacytools.io/my-thoughts-on-security/how-to-choose-a-secure-messenger

Its a step up from sms, but seeing how it has god awfull homegrown encryption, doesn't use end to end encryption by default, and doesn't even support e2e for groups or desktop, makes it god damn awfull in my opinion.