Foundation with Rails and Sprockets 4

The shift from Sprockets 3.7.2 to 4.0.0 has introduced some significant changes which currently break my foundation-rails installation. I have raised a ticket there, but it doesn’t look like issues like this are getting resolved at any great pace on that project. I’ve tried dropping the gem in favour of the yarn package, but there is little useful guidance out there on how to reconfigure everything to make this work.

Note that this is not a Rails 6 issue as such: I’m still on Rails 5 and using Sprockets rather than webpacker. I will probably try upgrading to Rails 6 with Sprockets soon, but this issue of Sprockets 4.0.0 will presumably still need to be solved.

The Rails world is in a bit of a mess over Sprockets vs Webpacker, and this is compounded for those of us using Foundation by the apparent lack of coherent solutions on both fronts. Would be grateful for any suggestions.