As most of us in this group probably already know, there's Ubuntu Touch, which I've seen on some phones, even being sold on ebay, on Pixel 3As. There's LineageOS & PostmarketOS, but they only run on certain phones, and the setup learning curve is challenging. And finally, seemingly the most popular one, GrapheneOS, only currently works on certain Pixel phones, but there is a partnership with Motorola, so we'll see how that goes. I don't know if any of these except Ubuntu Touch are considered Linux, though.