The moment I try to add any of my own REST services to the map it fails. I believe this must be related to cross-site issues. I can't add even a single feature layer without "Uncaught TypeError: FeatureLayer is not a constructor". I think this is because the page is not allowing me to access both ArcGIS.com functionality (the elevation profile tool) and my internal rest layers. While I am a novice developer I have successfully created several other pages utilizing featurelayers and dynamiclayers. I don't think I have any typos or syntax errors.
I see tons of sites saying that you can use "SameSite=None" somewhere but none of them specify where this might be set. Am I missing something? How do I allow both of these sites to be reached by my page?