Does the 'g' prefix do anything? On my Firefox it still searches for 'g com.scala.List' in Duck Duck Go, my default search engine. When I run that on Chrome it searches for 'com.scala.List' on Github because I've chosen g as a search leader for Github (which is super convinient and I wish I could do that on Firefox).

You definitely can do that on Firefox, in search preferences.

What other arcane commands do I need to use to make FF work like Chrome?

Why should Firefox work like Chrome? They're two separate products, and Firefox offers an explicit search bar for disambiguating searches from addresses. Especially important since 'List' could indeed be a TLD in the near future.

No reason to force X to work like Y.

The point of these commands (invented by Opera by the way) is to give you choice what search engine to use while not sacrificing your performance. Google's approach is different: remove choices that might confuse or distract you. Choose what you like.