In the second half of your Subnautica 2 gameplay, you'll be spending a lot of time in the Axum biome after crossing the gap with the Creature Leviathan in it. Unfortunately, there aren't a lot of sources for Fibrous Pulp here. You can get a few of them from the Freesia Flower, which is a small flower that you can find in some locations. Alternatively, you can head over to the Research Facility 1,290 meters in the eastern direction from the Lifepod at a depth of 127 meters to see some Lucifer Rotsac on top of it, which can also be harvested for Fibrous Pulp.