OpenAI has raised concerns with European Union antitrust enforcers over potentially harmful conduct by the likes of Alphabet Inc.’s Google, Microsoft Corp. and Apple Inc.The world’s largest startup recently took its gripes to the office of EU antitrust chief Teresa Ribera, highlighting “difficulties” it faces “in competing with entrenched companies” while pressing watchdogs to intervene to “avoid the lock-in of customers by large platforms,” according to notes on the Sept. 24 meeting....