I still today use, and hear familiar millennial use, “lmao”

Usually ironically with a twinge of negativity. Pronounced “luh-mow”

IE “Did you here the US elected Trump again?” “lmao”

Usually only used on its own, it suddenly sounds weird if you put it in a sentence but purely just used as a response to show ironic dissatisfaction quickly.

Pretty much the verbal equivalent of an eyeroll.