PEI is one of the best surfaces you will ever find to print on, although I believe one type of filament (I think a variation of PLA?) sticks too well and can damage the PEI trying to take prints off…

That’s PETG. I avoid using a smooth PEI plates like fire when PETG is loaded. Even after swapping the filament to PLA, little bits of residual PETG can still stick leaving a shadow on the plate. Textured PEI is mostly fine, but printing single layer stuff like brims is a pain to get off.