Rocket.Chat, MicroSIP, Signal, Facebook Messenger, Skype, Mattermost, Pidgin, Camfrog, CSipSimple, Adium, Tox, tSIP, Linphone, JumpChat, YateClient, Tor Messenger, Conversations, ArrowChat, Starfish PBX, Telephone, Caliopen, QuteCom, Quickchat, Voip Stunt, Shrtct, LekkerIM, Kaiwa, Vodia Networks, Vacuum-IM, Q-municate, Hyphen Messaging, Qnext, Profanity are some alternatives to YakYak.