What was the issue you encountered with private registries on Deno? Based on Deno's docs, it looks like they're supported[0]
[0] https://docs.deno.com/runtime/manual/basics/modules/private
[0] https://docs.deno.com/runtime/manual/basics/modules/private
//npm.pkg.github.com/:_authToken=${AUTH_TOKEN}
@myEmployer:registry=https://npm.pkg.github.com/
My impression is that the document you've linked isn't related to their NPM compatibility, but perhaps I need to look more into it.