BM Chat is described as 'localized ad hoc chat room that uses Mesh Networking via BlueMesh to transmit messages'. There are six alternatives to BM Chat for a variety of platforms, including Online / Web-based, Android, iPhone, Telegram and Facebook. The best alternative is Briar, which is both free and Open Source. Other great apps like BM Chat are Facechat (Free), NickEgo (Free), Bridgefy (Free) and WorldChat (Free).
An open-source decentralized and encrypted messaging app even without internet connection via Wi-Fi and Bluetooth. Messages are stored securely on your device, not in the cloud. Connect directly with nearby contacts - no Internet access is required.