Currently microsoft product line like SharePoint, Dynamics (Power Apps), Office, Teams, etc, etc is based on FluentUI https://developer.microsoft.com/en-us/flue

Currently microsoft product line like SharePoint, Dynamics (Power Apps), Office, Teams, etc, etc is based on FluentUI https://developer.microsoft.com/en-us/fluentui#/ https://developer.microsoft.com/en-us/fluentui#/ components that gives also the developers a close enough solution to extend UI within said products.