If you want a private desktop OS you either use a debloated Windows which can break, or Linux but it’s not always easy to use, but I’ve never heard of anyone use a de-googled Chrome OS, smth like Graphene OS but for desktops. I’ve actually never used Chrome OS but to my knowledge it’s open-source, easy to use and can already run Android apps making it a strong option
Chromium is FOSS that anyone can use and build upon but, primarily built by google themselves. Chrome is proprietary software that is owned by google.