The config auto populate for spawn eggs is having issues with these three mods and is only populating a portion of the item name/mob name.
https://gist.github.com/judicius96/6ac3d44b7c2dcd2f24210fe2e97586bc

When I attempt to manually correct or add the 20+ missing mobs from alex's mobs the mod says the partial entries are missing and "fixes" the config file.

If i turn the egg drop rate to 100% and kill a creature not listed (alex's mob emu for example) there's a console message saying the creature doesn't exist to drop egg.

Forge 36.2.34
Pack Builders Delight 2 version 3.7.2
Spawner Mod Version 1.8.14
Minecraft 1.16.5

Hi thanks for the issue, sorry for late answer.

This is caused by Alex's Mobs does not follow the Mojang naming convention for spawn eggs. Alex's Mobs uses: modid:spawn_egg_entity_name while Mojang standard is: modid:entity_name_spawn_egg. I might fix this but the best fix would be if Alex's Mobs would follow the naming convention.