For context, my organization has Hub Premium, and we also have an Open Data Portal dating back to before Premium existed.
Whenever someone who is currently logged into ArcGIS Online through a public account tries to view either our Open Data Portal or our Premium initiative, they get either a 404 error or a plain white screen. The console shows errors reading "Uncaught TypeError: Cannot read property 'indexOf' of undefined". I haven't been able to test whether the same issue happens for people logged in with accounts from another organization. If they log out of ArcGIS Online, they can access our Hub sites without issue.
Has anyone else experienced this kind of issue? Have you found a workaround? We're trying to promote our Open Data Portal, and it's not an insignificant problem if people who already use ArcGIS Online get blocked out of accessing the open data.
For reference, here is our Open Data Portal: SEMCOG (Southeast Michigan Council of Governments) Open Data