Like you'd expect, you can trade with Piglins in the same way you trade with them in vanilla, with Gold Ingots.
Piglin
You can find Piglins in almost every biome throughout the Beneath.
Trade Results
1 Copper Ingot
1 Tin Ingot
1 Silver Ingot
1 Bronze Ingot
1 Bismuth Bronze Ingot
1 Cast Iron Ingot
1 Zinc Ingot
1 Brass Ingot
1 Bismuth Ingot
1 Nickel Ingot
1 Cinnabar Gem
4-6 Sulfur Powder
1-2 Leather
6-12 String
6-12 Nether Quartz
12-18 Mangrove Lumber
6-8 Mangrove Logs
4-6 Cooked Venison
4-6 Ghost Peppers
4-6 Gunpowder
4-8 Charcoal
6-12 Arrows
6-12 Flux
8-12 Pyroxenite Bricks
8-12 Migmatite Bricks
8-16 Sticks
Bastions
Raiding a Bastion might be very dangerous, but they can also be very rewarding! You can find things like:
Gold, Rose Gold, Pig Iron, Black Bronze, and Silver ingots
Black Bronze weapons, tools, and armor
Kaolin clay and graphite
Permanent light sources
Cloth, leather, seeds, and food
And other treasures!
Piglin Disguise
If you want to ensure an easy time trading--or simply mingling with the locals--Put on a Piglin Disguise to prevent Piglins from being hostile with you on first sight. But beware! They only put up with so much...