Search all pieces of jackfruit and remove any seeds found. Slice off the hard triangular "cores." Discard about half of these hard triangular pieces, and the rest slice small and keep with the jackfruit.
Mix together the poultry seasoning, celery salt, and garlic powder in a large mixing bowl. Place jackfruit in the mixing bowl and toss until each piece is covered with the seasonings.
In a large skillet, heat 2 tablespoons olive oil over medium heat. Once hot add the onion, celery, and garlic. Sauté until onion and celery are soft, about 3-5 minutes.
Dissolve 3 (or 6 — see notes below ingredients) bullion cubes in 3/4 cup hot water. Pour broth along with the jackfruit into the skillet. Stir well, cover, and turn heat to low. Keep at a light simmer for 30 to 35 minutes, stirring every now and then. (I used this time to start preparing my stuffing.)
Remove lid from skillet. Shred jackfruit pieces, using two forks. If you come across any hard chunks, smash these down with the back of the fork to soften.
Dissolve the last of the bullion with a 1/2 cup hot water. Pour broth into the skillet and turn the heat back to medium. Keep the heat up and stir frequently, until liquid is dissolved. Remove from heat.