Issue description:
Was it changed to another material? Placing lapis into the Tinker Anvil along with a tool used to work to get the luck modifier. I tried using other materials like redstone and they worked fine.
If crashed, link to crash report (use a site such as pastebin):
No crash
Versions:

• Minecraft: 1.16.5
• Forge:
• Mantle:
• Tinkers Construct: 3.0.2

Confirm below that this issue is not covered on the roadmap or "Whats New?"
It isn't, it says the luck modifier should be in, and I have seen it used on youtube videos, it doesn't say if the material has been changed though
Can it be reproduced with just Tinkers Construct? If not, list the other mods required to reproduce the issue.
Playing in the All The Mods 6 modpack
Should be fewer than 10 mods, you should be running no mods besides those 10 when you reproduce the issue.

Yes it was. Check the JEI modifier tab.

How do I do that? I tried checking in the Materials and you book and that modifier is absent

Check the JEI modifier tab.

Same way you check any other recipe, usage on an input (such as a tool), or view all recipes

Ok, thanks so much, I figured it out, I didn't know I could do that so it should help with other modifier recipes too, thanks bruddah, you a real G