Dude I didn’t even know that flag existed until we started looking into this. So as much as it might not be what you wanted to hear, “check out the esbuild docs” ended up being the correct solution. 
I agree, and I have opened a PR Add external flag to esbuild for fonts and images by mcrumm · Pull Request #4536 · phoenixframework/phoenix · GitHub
Please try to remember that we are all people, and for the most part all of the work happening here is volunteerism. Sometimes we miss stuff. Sometimes we find better solutions later. It’s all iterative. Have a good one!
