If you want a top-end starting quarterback in free agency, good luck.
Kirk Cousins was a weird outlier in 2018. The Washington Commanders couldn't sign him to a long-term deal, he played on some franchise tags and then hit unrestricted free agency at age 29. Unless a quarterback is aging, injured or ineffective, they practically never hit free agency at a prime age.
There are some options, usually backup-level players trying to hang on or once-starters looking to resurrect their careers. The latter worked out for the Tampa Bay Buccaneers when they signed Baker Mayfield last year.