I could have sworn fireplaces worked as a heat source for cooking. No? I thought I remembered making charcoal using the fireplace. But maybe I was making potash standing at water source that's near the fireplace. I can't recall anymore.
Many heat sources changed recently when they made it so you cant cook on a forge.
The heat source that can be used depends on what you are cooking. I don't think the fancy fireplaces ever counted as one. A forge is fine for items that are in the barbeque list, but you need an oven or the vet reward bbq for baked items. I believe the different heat sources are listed on the cooking page of the wiki. I know I have made potash recently using a forge.
Sadly the alchemy menu does not accept the veteran reward BBQ as a heat source for potash.
If it's working for fish pies, then it is counted as a fire source and should (I think) make charcoal. I think you could probably put that one in the bug forum.
I'm not aware of any heat sources being changed recently. Maybe I missed that one?
For making charcoal I tried the fireplace (which I swear I used before to create charcoal), the stone oven, the home hearth, the wood stove and the elf oven. I didn’t try a forge or the old trick with the alchemy burner, campfire with kindling, the BBQ or anything else I may be forgetting.
Neither the home hearth, wood stove or fireplace worked to produce charcoal. The stone and elf ovens worked. I double checked on the fireplace, wood stove and hearth to see if I could cook fish steaks. I was successful.
I can’t say if there are any other items on the cooking menu that you can no longer use the fireplace or home hearth for. Or if any other items from the menu can’t be produced on the new wood stove. But in my opinion we should be able to use the fireplace, hearth and wood stove for all items on the cooking menu. To not be able to, creates restrictions that make no sense and makes using these various items to decorate with less functional and less appealing.
I did submit a bug report, hoping the changes are accidental. I can’t see what purpose the changes serve if they were made intentionally.