Was hoping to be able to include this in my playthrough in combination with Brevven's mods (e.g. lead - https://mods.factorio.com/mod/bzlead). Running into an issue where electric furnaces don't have recipes for smelting his added ores when space age overhaul is enabled. Checking FNEI shows that the recipes for smelting lead ore exist for the stone furnace and some furnace entities added by mods, but not steel or electric furnaces.

Commenting out this line in data-final-fixes.lua resolves this issue, though obviously doing that prevents the advanced/more efficient steel, copper, iron, stone brick recipes from being selectable in that entity:

data-final-fixes.lua:data.raw["assembling-machine"]["electric-furnace"].crafting_categories = {"advanced-smelting"}

Wondering if it's feasible to copy over all existing recipes from whatever the original category is to the advanced-smelting category and then remove the original steel, copper, iron, bricks recipes (that you want to replace) and then add in the advanced ones instead of just starting from an empty category and adding the advanced recipes, in order to catch any relevant recipes that have been added by other mods? Wouldn't really have a clue how to start with that or I'd give it a try myself.

Thanks for the feedback about this issue with bz mod, my lua writing skills were not great when I started working this mod (my first one :D). Better code compatibility is a plan but I do not currently have time to actively work on it.

Given your description, issue is very likely due to a particular crafting category (which is a set of recipes) not enabled on some furnaces
Thing is, by default, furnace entities only support auto-selected recipes from the "smelting" crafting category.

To prevent some issues with that (coal being both a fuel and an ingredient in particular), Space Age Overhaul convert the base game furnaces into assembly machines in data-final-fixes, which support selectable recipes.

data.raw["assembling-machine"]["electric-furnace"].crafting_categories = {"advanced-smelting"} then forces only my new "advanced-smelting" recipes to show up on the electric furnace.

You may edit that with something like :
data.raw["assembling-machine"]["steel-furnace"].crafting_categories = {"smelting", "advanced-smelting"}
data.raw["assembling-machine"]["electric-furnace"].crafting_categories = {"smelting", "advanced-smelting"} to keep showing all smelting recipes on them as well.
If bz adds lead recipes under this "smelting" category, this should work, if it adds custom categories, edit the above line accordingly.