Do you guys have any idea whether the custom WhatsApp apps like GB, FM will support this new end to end user encryption or not?
WhatsApp has started providing end to end encryption for user who have upgraded to their latest version. I can see following message in yellow mark as soon as I open any contact in whatsapp
"Messages you send to this chat and calls are now secured with end-to-end encryption. Which means WhatsApp and third parties can't read or listen to them."
Use Signal app. It encrypts your calls and messages with end to end encryption by using a protocol that many in the security field greatly appreciate.
Whatsapp collaborated with the creator of Signal to incorporate the latest security features in their app.
Stay away from Telegram and other apps that claim to be secure. They are not!
Also you really can't be any secure on a smartphone.