By "Linux phone", what are your expectations exactly? Because if you talk "only" about the userspace, I have been daily driving Ubuntu Touch since 2019 on a Fairphone 2 and then a Pixel 3a and it is working like a charm. But it is using halium so you still have an Android kernel. So if you also talk about the kernel then yeah Postmarket OS is the closest to this and quite good on Fairphone already, I think some people could daily drive it if they feel adventurous. Then if you talk about 100% free software then indeed, nothing with a working modem is available as far as I know. And if you talk about open hardware then we are clearly not here even if I dream about it...