Hi!
1. Copy the below URL link and paste it on your browser.
https://services.arcgisonline.com/arcgis/rest/services/World_Imagery/MapServer/
2. Open QGIS Data Source Manager (as you already knew this).
3. Go to ArcGIS REST Server and make a new connection and use the above URL link.
If you succeed, add a file to your screen and enjoy working.
If the ArcGIS REST Server does not exist among the list, make a new connection with ArcGISMapServer, which is often located on the same place as ArcGIS REST Server appear.
Tile Mapping Services does not work the same way as ESRI REST and OGC. I think this issue has created problem with your download.
Good luck.
Best, Faiez