SharePoint Add-In retirement in Microsoft 365

BertJansen & EinmalIM 

We also see that using an Azure AD app with sites.Selected permissions enables us to create a RER which fires without ACS.

We took these steps:

1. Create an Azure AD app with sites.selected permissions on SharePoint api
2. Create a certificate and add to the app
3. Add fullcontrol permissions for the app with Grant-PnPAzureADAppSitePermission on my site collection
4. Log in with PnP.PowerShell using Connect-PnpOnline [tenant.sharepoint.com] -ClientId [clientid] -CertificatePath c:\temp\certs\test.pfx -CertificatePassword $password -Tenant '[mytenant].onmicrosoft.com'
5. Add a RER to my list using Add-PnPEventReceiver
6. Host the RER locally using devtunnel or Ngrok

We see the RER firing after this. I can manipulate the item, execute other logic and return a SPRemoteEventResult

The only thing I am worried about is a error message in the request headers:

"The app i:0i.t|ms.sp.ext|[clientid]@[TenantID] does not have an endpoint or its endpoint is not valid"

We really need sync events because we need to provide the users with input when they upload or configure something wrong.