I'm not entirely certain about ESM support; if only because migrating from commonjs to ESM is often an all-or-nothing approach.
IIRC once you are in ESM-land, you can easily import other ES modules, and you can import commonJS modules, but your own exports cannot be imported by commonJS files.
That causes a significant issue in that many plugins (still written in CommonJS) will try to require ESM-ified libraries in NodeBB and promptly crash.
While I am reasonably certain there is a way forward (via some sort of shim, etc.), that might require the talents of people smarter than me (like @baris, @pitaj, or @oplik0 😄 )