Not my first libre product, but definitely the one that got me into searching for libre alternatives - OpenOffice. Despite not being great at the time (or ever), i was amazed by how complicated microsoft turned 365Office into. I suddenly had to buy subscriptions to all of the office products for outrages prices just so that i can have a simple words editors? Screw that, i googled for “open source office software” and never came back to m$Office.
There is a software called “wine” that is used for running windows apps on linux. Proton is a version of Wine that specializes in running video games.