Convert domain to IP address, then lookup IP address will show you ISP ( internet service provider )
A sample arcgis online
https://services.arcgis.com/f48yV21HSEYeCYMI/arcgis/rest/services
https://transparentgov.net/json2tree/esri/server/folder.html?org=https%3A%2F%2Fservices.arcgis.com%2Ff48yV21HSEYeCYMI%2Farcgis%2Frest%2Fservices&url=https%3A%2F%2Fservices.arcgis.com%2Ff48yV21HSEYeCYMI%2Farcgis%2Frest%2Fservices&select_folder=8&select_layer=0
Convert domain to IP address
lookup IP address will show you ISP