Yac - Take your time back from Zoom & Slack
Slack - A messaging app for teams who see through the Earth!
9mCollab - Collaborate (efficiently) Conclude (fast) Contribute (in the knowledge base)
LinkedIn Voice Messaging - Communicate when you want, how you want
Mattermost - Mattermost is an open source alternative to Slack.
VoiceMo - Send your voice messages in an exciting new way!