Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Yac - Take your time back from Zoom & Slack
BuildFire - BuildFire is the easiest way for small businesses to build a mobile app in a matter of minutes for iOS and Android.
Beseda - Async video and audio messaging for remote teams
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
SuperNormal - Async video updates for remote teams