Thanks for doing this!
I work at Grist, and we see a lot of self-hosters activating and using our Enterprise features. An extra build step is needed to include that option. If you added:
yarn run install:ee
just before:
yarn run build
Then Grist would build just as it does now, but there would be an extra toggle available in its admin page to turn on enterprise features if the end-user wants that. Most self-hosters quality to use those features for free.
Just a thought. Happy to help if there are any other packaging issues. I'd suggest (if you haven't already) checking the /admin page for all self-diagnostics, such as checking that sandboxing is working.