As title says it is possible to steal stuff from bastion chest by using tnt or hoppers without trigger piglins.
link to demostration: https://www.youtube.com/watch?v=icSSaEig1u4
You are able to get items from a chest with a hopper, without agroing Piglins
Piglins will not attack you if you indirectly explode their loot
piglin base / chest
Hoppers used to raid Bastions.
Piglin can't angry by player openning hopper.
If you use a funnel to take items from a chest in the Nether Bastion, the piglins will not attack you