Web appbuilder app, use javascript api version v3.25. As long as you see version v3.xxx, that means it is web appbuilder ( retired 2024 ). As long as you see version 4.xxx, that means it is experience builder.
https://maps.octa.net/octasepviewer/
Both domain are identical point to same Arcgis Server ( Arcgis portal Enterprise )
https://maps.octa.net/arcgis/rest/services
https://gis.octa.net/arcgis/rest/services
3 panel system
https://transparentgov.net/json2tree/esri/server/folder.html?org=https%3A%2F%2Fmaps.octa.net%2Farcgis%2Frest%2Fservices&url=https%3A%2F%2Fmaps.octa.net%2Farcgis%2Frest%2Fservices&arcgis_online_token=&select_folder=67&select_layer=17
2 panel system
https://transparentgov.net/json2tree/esri/server2/folder.html?org=https%3A%2F%2Fgis.octa.net%2Farcgis%2Frest%2Fservices&url=https%3A%2F%2Fgis.octa.net%2Farcgis%2Frest%2Fservices&arcgis_online_token=&select_folder=226&select_layer=
orange county Arcgis Server ( Arcgis portal Enterprise )
https://www.ocgis.com/arcpub/rest/services
https://transparentgov.net/json2tree/esri/server/folder.html?org=https%3A%2F%2Fwww.ocgis.com%2Farcpub%2Frest%2Fservices&url=https%3A%2F%2Fwww.ocgis.com%2Farcpub%2Frest%2Fservices&arcgis_online_token=&select_folder=271&select_layer=0
orange county arcgis online
https://services3.arcgis.com/hPs600I3X0RTaaaq/ArcGIS/rest/services
https://transparentgov.net/json2tree/esri/server/folder.html?org=https%3A%2F%2Fservices3.arcgis.com%2FhPs600I3X0RTaaaq%2FArcGIS%2Frest%2Fservices&url=https%3A%2F%2Fservices3.arcgis.com%2FhPs600I3X0RTaaaq%2FArcGIS%2Frest%2Fservices&arcgis_online_token=&select_folder=243&select_layer=0