I tried create same world (same seed) from 1.15.2 in latest snapshot to see new nether biomes. I have in nether quite big fortress and few more around, after creating this world in snapshot, I could not find any fortress at all. Maybe its unlucky seed.
Map seed: -5864750446916034486
Nether coords: x847 z880
Duplicate of MC-171017 - nether fortress generation has changed since 1.15.2.
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