Hello,
Recently my embedded map viewer classic products have ran into authentication issues, and a new popup urging an upgrade to the new map viewer that ruins the experience. This is following an organizational upgrade to from 10.9.1 to 11.3
If I choose to embed the new map viewer product, it's lacking the mapOnly URL parameter.

And if I can't hide the details and layers and all the junk that I don't want to see, then I'm left with all this junk opening like this:

in comparison to the map viewer classic:

Wow, so clean on load!
So you're probably going to suggest using the Embed URL parameters for webmaps...

It doesn't seem fully supported, as each way I try to construct an Embed parameterized URL to focus on a subset of layers I'd like to embed, it returns the original layer exposed when the webmap was published.
So, my simple ask: How do I properly structure my URL to generate a webmap with a particular set of layers, with the details, layers, legend, etc all hidden in a "mapOnly" format?
Original URL: https://{domain}/arcgis/home/webmap/viewer.html?layers={layer_id}¢er={lat},{long}&level=16&mapOnly=true
Thanks for the support,
Jack