The user-generated "Celestial" or "SparkFun" and "AdaFruit" libraries are widely shared on forums. You can find them via:
Community libraries often have mismatched pin mapping. A transistor might have collector and emitter swapped. A 100-pin QFP might have the origin in the wrong corner. Always, always audit a component before routing 50 wires to it. download full library for altium designer