Hi guys, I just proposed a step-by-step solution last week to deploy the whole customised widgets App of ArcGIS Experience Builder on ArcGIS Portal directly (not just "add an item", but put and use the customised widgets on Portal Directly). Before ArcGIS proposes the ultimate solution you could use this to deploy your whole ArcGIS Experience Builder with customised widgets on ArcGIS Portal Enterprise.
So far no other internet resources talking about this small trick (100% innovative and it works), really want to share this with every Experience Builder Customised Widgets Developer, please take a look on my video, if not working, just come back and blame me. Please share this to your Esri community, and don't forget click like and subscribe if you think it's useful thanks.
https://www.youtube.com/watch?v=fDN7rr5259w