i started a new world earlier with the brand new update with no other mods and noticed that there were hardly any mobs spawning. there was an abundance of catfish, but hardly any others anywhere else. normal minecraft mobs spawn, but even in a desert there was absolutely nothing. again i just downloaded the 1.20.1 update with citadel, the newest version of forge, and ive run it with no other mods to the same result. thank you for your help!

I have the same problem here,and I have edited the config;it doesn't help

Similar issue here, I checked the config file, but it appears to be set up properly or at least is in line with 1.18's. However, I believe my issue is slightly worse than than the one you've described, multiple biomes are now vast waste lands with no signs of life anywhere (Deserts, Jungles, Snowy planes, Tundra and Dark oak aside from the hostiles) and even at night the hostile mobs are few and far between. The game is now set up with a minimum of 8 to a maximum of 32 mobs within the players 128 block mob generation distance which is being split into hostile, friendly and passive mobs both at and below your Y level like usual which makes it hard for the game to properly populate above ground areas.

This^ is vanilla

Modded is even worse, nearly all of Biomes O' plenty's Nether Biomes are lifeless, Nether particles have gone nearly extinct (which is odd seeing as this mod shouldn't be able to affect that), all of the new overworld biomes are empty, custom mineshafts are turned back into vanilla ones (Hopo's mineshafts, which was mentioned in another bug report, hopo's other structures are unaffected though) and are completely dead to the point that no vanilla mobs will spawn in them, even cave spiders spawners are broken though you can fix it by simply moving the spawner in creative. Other mods that add hostile and passive mobs specifically will slowly begin to stop working until nothing from them spawns anywhere which occurs after 20 in game days (mods: the graveyard which adds both hostile mobs for the general environment and for custom structures and friendsandfoes which adds all of the canceled minecraft mobs), friendly and neutral mobs are unaffected aside from the max spawn count forcing them to fight with the vanilla mobs for the right to spawn in.

The mod however is functioning at least in some capacity, random catfish can be found alone in rivers which are otherwise devoid of fish and populated by small clusters of squids like an old console world. Buffalo, the black Kiwi bird thing, Grizzly bears and underminers have appeared on their own without any other mobs around them when I use the teleport command or use my map mod (journeymap) to travel ~1000 blocks or more but after that it'll be vanilla mobs or nothing if the biome is one of the above types (mineshafts can only receive a miner once when they generate, after that teleporting will have no affect. explored areas will not allow any of your mobs to spawn, the area must be newly generated chunks). So aside from catfish, which are rare unless you go below Y level 2 (ideally you want to be well into the deep slate layer and find a large water pocket), the world is basically devoid of your mobs without teleporting vast distances.

Loved getting to use this mod in 1.18 for the first time a few months ago, it made the game feel way livelier but now, it's quite the opposite. Also OP has any other mod been affected on your end? and are their more dead biomes or just deserts?

Edit: forgot to add oceans to the list of vanilla biomes, all types, not even the old squids or the drowned spawn out there in the watery void.

I've had this same issue while running with and without other mods installed, and have only been able to find the Grizzly Bear, hummingbird, crimson mosquito, warped toad, blobfish, cachalot whale, frilled shark, frost stalker, giant squid, Rhino, sugar glider, and the skreecher. I've investigated almost every biome and have been left in a world devoid of the life promised by this mod. hopefully, the next update fixes this!

Same issue here. With mods or not. I'm on 1.20.2 version. Only few species spawn like rhinoceros, whales and frosttalkers spawn normaly. Other don't spawn. In the nether too much crimson mosquitoes. Maybe about ten per chunk. few soul vultures are here.

Something else. I wanted to understand why it wasn't showing up. I used the eggs of animals that did not appear. it worked but it created big lags on the game only when looking in the direction of the animal. tested with crocodile and tiger. May be part of the problem.

I hope i could have helped !