I tried going in a copy of one of my main worlds and there I had the old nether chunks already loaded. When I did the /locatebiome for any Nether Related biome, it gave me completely random co-ordinates and did not teleport me to the place I was looking for.
Linked issues
Comments 3
Duplicate of MC-184059
I wrote something similar about /locate command, which cannot locate Fortresses and Bastions generated before 20w19a/20w20a-b. Probably this is another consequence of the bug that's happening.