Microsoft recently added new Modern Sites. These new sites take advantage of the new modern pages and other features. The only issue with these sites is that they have Custom Scripting turned off by default even if you have turned it on in your tenant settings. Custom Scripting needs to be turned on in order to install and use LiveTiles. Check out Prerequisites - LiveTiles SharePoint Installation for more information.
To enable Custom Scripting for Modern Sites to install and use LiveTiles on those sites, you can so by completing the following in Powershell:
Download and Install the SharePoint Online Management
Make sure that you are on a computer running Windows.
Go to this site.
Download and Install the SharePoint Online Management Shell.
The SharePoint Online Management Shell is used to connect to your SharePoint Online subscription via Powershell.
Enter URL for the SharePoint admin site: https://<yourdomain>-admin.sharepoint.com
Enter tenant admin username and password:
Type in the following command adding the URL of the Modern Site.
Set-SPOSite -Identity https://[yourtenant].sharepoint.com/[siteurl] -DenyAddAndCustomizePages 0