Standard AGOL esri hosted feature service structure:
https://services[1 to 10].arcgis.com/[organization's ID]/arcgis/rest/services/
As long as you know organization ID and services{?} number, you find it.
To find services{?} number, you can google search organization ID and arcgis rest
Step 1.
download organization id from
Esri's entire customer list revealed ( ArcHub )
CSV file direct download from here
https://transparentgov.net/data/json2tree/hub_v1_created_before_2025_3_26.zip
or
https://transparentgov.net/data/json2tree/opendata_v3_created_2017_01_01_to_2025_03_29.json.zip
Step 2.
shortlisted Esri's customer who had an established GIS asset
https://transparentgov.net/data/json2tree/opendata_refined_2017_to 2025_Mar26.zip
https://transparentgov.net/data/json2tree/hub_refined_2017_to 2025_Mar26.zip
Step 3.
looking for organization ID column, copy the org-id, pasted in google search
for example : I randomly pick a org-id is
cakQzytYZtvfbh5z
Step 4.
google search organization id and 'arcgis rest", cakQzytYZtvfbh5z arcgis rest
you will find the top result is what you looking for,
https://services.arcgis.com/cakQzytYZtvfbh5z/ArcGIS/rest/services
Step 5.
google search organization id and "rest/services", also works: cakQzytYZtvfbh5z "rest/services"