I kept having errors when using the App Designer in versions 4x:
objects are not valid as a react child (found: typeerror: cannot read properties of undefined (reading ‘find’)). if you meant to render a collection of children, use an array instead.
It looks to be solved by installing .Net Framework 4.8 on the server hosting PowerShell Universal. If this is a requirement, maybe it is better to update the page System Requirements - PowerShell Universal to reflect this.
Product: PowerShell Universal Version: 4.0.7