If you are interested in a spawn spot with an abundance of mobs, then try this seed with three spawners at the start. They are quite deep, you have to go down at -88 14 245. Here you will find three treasures with spawners of zombies, skeletons and ordinary spiders. Also you will find six chests with valuable loot, among which are gold bars, horse armor, a saddle and much more.
Screenshots:
Seed ID
For Minecraft 1.15.2/1.14.4:-863807451573770116