Why would anyone need to manually update the phone from a terminal Window? Like Android, the phone will notify you when updates are ready. Then all you need to do is tap to allow the update. For things that the phone will do for you, you’re better running with the pack. If Purism accidentally pushes out anything harmful, the first few people who are affected will complain. The problem will then be fixed, probably before you can even be affected. You could probably recompile the kernel yourself too. But why would one need to do that? Keep everything easy until you can’t do something that you want to do through any other means.