Official support for mainstream apps like Viber and WhatsApp has ended. However, hobbyist developers have created third-party J2ME clients for modern protocols like Discord (discord-j2me) and XMPP (miniim). These require manual installation and are community-driven, so they may have varying degrees of stability and features.
A common confusion arises because (pre-10) and Nokia Symbian (S60v3/v5) also used Java at their core. However, these were advanced Java-based operating systems with richer APIs than standard J2ME. Viber For Java J2me
Officially, Viber Media never released a fully functional, standard J2ME version of its application that supported voice calling. While they did expand to platforms like BlackBerry OS, Nokia Symbian, and Windows Phone, standard Java ME platforms presented severe technical limitations: Official support for mainstream apps like Viber and