Wire is a option (https://wire.com/en/ https://wire.com/en/). It can be signed up to with a email adresse and does not need a phone. The web interface is pretty

Wire is a option (https://wire.com/en/ https://wire.com/en/). It can be signed up to with a email adresse and does not need a phone. The web interface is pretty simple. https://wickr.com/ https://wickr.com/ could also be a option, its free for up 2 30 users but as it does more the interface is also more complicated.