I have some kind of bug 1.20.1 Forge, the mod items are missing from the recipes and menu of the creative mode.

Just to make sure: Chimneys are part of a Functional Blocks creative tab. Recipes are unlocked when player obtains specific items (bricks, stone, cobblestone, etc).

If it's indeed not working correctly for you - check logs, check if it works with only Sooty Chimneys installed (without other mods) and provide all info you can give to reproduce the issue.

I can confirm that this mod is not showing up correctly in a modpack setup, it only works when by itself as OP mentioned for me.
There is still no mod tab when loaded with mods or in the creative search menu.
Searching logs does not reveal any errors either. I can upload a copy of my log for analysis if it'll help.
Forge 1.20.1 - 47.2.0
Mod version: v1.2.1

@NovaLynxie If everything works with only sooty chimneys - it's most likely other mod that's causing it. You can try disabling mods in parts to isolate the conflict.