I've been using the mod on a server with friends and I have been unable to obtain the biome specific crates/fish without using the /fish command. Everything else works fine, it's only the swamp, ice, and soul sand valley fish/crates (which I think are the only biome specific ones) that seem to be unobtainable.

Biome-specific fishing has been fixed in the next update, thanks for the report.

Do you have another fishing mod installed, such as Netherite Plus?

I actually did have that installed, although I tried removing it and just using this mod in a new world and I got the same results

I mean, if you want to overwrite netherite plus's fishing mechanics by default, go ahead, yours are much better.
I'm soon going to try biome specific fishing with just go fish & a few other mods.

latest.log
I doubt this will help but i fished a few times.

latest.log
this is the latest log for the server. prolly won't help either.