We had ArcGIS Enterprise 10.8.1 installed on a disconnected environment, and we changed the base map gallery settings to read from custom group contains list of custom base maps.
The issue is that when create a new experience builder app, adding a map widget and enable base map gallery option , The base map gallery widget is not able to load the local base maps and show "No basemaps available" label, and when tracing requests initiated from browser developer tool found that the widget on open initiate request to ArcGIS online and fail, So what could be the issue and is there any configurations missing.
Note : This issue is not exist when create web app builder app it can read the local base maps.
Thanks for letting us know. We are looking into it. Meanwhile could you please log in an issue to Support?