Enderyoink
Fully server-sided mod that allows endermen to pick up any block. They'll also drop unobtainable blocks that they're holding, such as bedrock and budding amethyst.
This is not done via a datapack, it's done through mixins, so it's technically compatible with any mod. I did not test this with any mods however, and it almost definitely causes severe issues with many, so do NOT install this mod on anything you care about!
I might update the mod to more versions later, but don't count on it, as it was just made for fun and for practice.
Endermen holding obsidian and end stone on the main end island.
Look at them, leaving all the trees floating >:(
Two endermen in the nether wastes, holding fire and netherrack respectively.
Enderman in a dungeon holding a spawner
An enderman in a deepslate cave, holding diamond ore.
This is NOT a feature of the mod, this was a world made to test during development, and I'm using it to showcase them picking up unbreakable blocks.