aTox is described as 'free open-source messaging app for the Tox protocol'. There are more than 10 alternatives to aTox for a variety of platforms, including Android, iPhone, Android Tablet, Mac and Windows. The best alternative is Signal, which is both free and Open Source. Other great apps like aTox are Tox (Free, Open Source), FluffyChat (Free, Open Source), Status (Free, Open Source) and Antox (Free, Open Source).
Signal is a messaging app with an unexpected focus on privacy, combined with all the features expected from a modern IM app. Signal has received a lot of praise from all around the world for its security and privacy-respecting technologies.
FluffyChat is an open, nonprofit and cute matrix messenger app for Ubuntu Touch, Android and iOS. Open Opensource and open development where everyone can join. Nonprofit FluffyChat is donation funded. Cute ? Cute design and many theme settings including a dark mode.
Olvid, the most secure messaging app in the world. Olvid guarantees the total and definitive confidentiality of exchanges, relying solely on the mutual trust of interlocutors. For the first time, security does not rely on trusted servers.
It uses the Tox protocol which is Peer to Peer, it will have a higher battery usage than other Messenger apps. If you are stuck with Antox or uTox (µTox) for Android, try this Tox Client that was especially optimized for Android.