We have assign the App to the selected SharePoint Site by using PnP PowerShell and now pnp removed that support. Is there any other way we can assign permission to a particular user to access the selected SharePoint site? We have referred to the link below to assign permission using Powercell.
https://medium.com/@sanghuynh_73086/how-to-access-sharepoint-site-using-microsoft-graph-08d20311c61c#:~:text=2.2.-,1.,Sharepoint%20Site%20(selected%20site)