Comment by hollerith

It is relatively easy to make a secure OS. What is terribly expensive in developer labor is a secure OS that runs a mainstream browser well. Android is an open-source OS that runs a mainstream browser well and is about 100 times more secure than any other open-source Linux distro -- except ChromiumOS. But for some reason, no vibrant open-source project ever formed around ChromiumOS whereas a vibrant open-source project (namely GrapheneOS) has formed around the Android open-source project.