Forum Discussion
Install Add-in in Site Collection from App Catalog using CSOM and Powershell
How to install Add-in in Site collections from app-catalog by using powershell OR CSOM without enabling SideLoading feature ?
You will want to look in to the ALM APIs. Currently it's built on REST, but there are CSOM extensions like PnP or Office365 CLI that can help with this.
Check out this documentation for how to install apps from the App Catalog.
https://docs.microsoft.com/en-us/sharepoint/dev/apis/alm-api-for-spfx-add-ins- AFAIK, you need to enable sideloading in order to be able to install de Add-ins in the site collections
