What are some alternatives?
When comparing Microsoft PowerApps and AppSheet, you can also consider the following products
Fuse - Fuse is a UX tool suite for mobile app designers and developers.
Dropsource - Mobile development platform for building native iOS & Android apps
Siberian CMS - Siberian is an Open-Source and Free App Maker. Unlimited Push Notifications. Unlimited features. Fully Customizable. Download it and build your own app now!
GoodBarber - GoodBarber is a mobile app creation platform.
Bizness Apps - Create your own app or become a reseller and build apps for others
Mobidonia - Native mobile app builder for iOS, Android & Apple Watch