Liquid fuel powered furnace. Allows the high-temperature purification and transformation of raw resources into refined minerals
Mods introducing new content into the game.
Things related to oil and other fluids.
Furnaces, assembling machines, production chains.
Changes to power production and distribution.
Some mods, like Krastorio 2, change the electric furnace from a furnace to an assembling machine.
I've opened a PR here that addresses this, and also updates a few other 2.1 migration pain points.