Firefox 100 includes subtitle support for picture-in-picture video https://apple.news/Aw0ho-ZAKT_m8qgxvEcm_0A
Google and Mozilla are ready for Chrome and Firefox version 100 to break some websites https://www.theverge.com/2022/2/17/22938721/chrome-firefox-edge-version-100-websites-bug-compatibility-issues-mozilla-google-microsoft