• coral_blocks cannot be send to furnance burning slot with pipes
• dried_kelp_block and bamboo are not led to the fuel slot with pipes

What are coral meant to do in the burning slot? The MC wiki makes no mention of this on the smelting page - https://minecraft.gamepedia.com/Smelting#Recipes

uff... i forgot that this was a local change >.<

sorry, leaving the other two ...

In that case it’s already fixed

If a datapack provides recipes, is there a way to check whether a furnace will accept an item that you could use?

Not with Spigot, the recipes API is currently not fully functional and hasn't been for a few years.