@awesomerobot I have followed the instructions in your post to the best of my (limited) abilities, and am running into several things, only one of which is to do with the change in Font Awesome icons, I think. But let’s deal with that here.
Here is a screenshot of what’s going on in the console:
Focusing on the Deprecation notice, it seems that the icon "search’ is an issue, with the new icon named “magnifying-glass”. A search for “search” in the developer tools search function returns (unsurprisingly) many results - (6,504 matching lines in 278 files) - and I really cannot see the wood for the trees. But I can say that there is NOTHING like the results displayed in your original post, paragraph 3!
Your suggestions of how to track down the component causing this issue would be gratefully received!
I will post about the emberjs issue in another post later.
Thank you - Discourse is normally a breeze, but this has me flummoxed.