What do you mean? Can you be more clear?
nostr:nprofile1qy2hwumn8ghj7un9d3shjtnddaehgu3wwp6kyqpqhzz35pkl67w53lpj2g62zh56g63j5zvz4q3m2nxlsfg5hxcjpwssp9zrag nostr:nprofile1qy2hwumn8ghj7un9d3shjtnddaehgu3wwp6kyqpql7j9s2znwsfcezul4635gnezjg52t7x88efrdehm8h5sp7r6yu4qug8lkv They're portable computers which happen to have cellular. The portable computer part is crucial for privacy since carrier-based calls/texts are horrible and should be avoided along with wanting to support things like running a Bitcoin wallet, browser, etc. Existing mobile software is near entirely written for iOS and Android, and other platforms aren't serious.
Discussion
nostr:nprofile1qy2hwumn8ghj7un9d3shjtnddaehgu3wwp6kyqpqhzz35pkl67w53lpj2g62zh56g63j5zvz4q3m2nxlsfg5hxcjpwssp9zrag nostr:nprofile1qy2hwumn8ghj7un9d3shjtnddaehgu3wwp6kyqpql7j9s2znwsfcezul4635gnezjg52t7x88efrdehm8h5sp7r6yu4qug8lkv It's largely the same thing as building an open source OS, hardware and firmware for a laptop and desktop. The smaller form factor doesn't really change that much about it. They're just computers. Cellular is one of the radios alongside Wi-Fi, Bluetooth, NFC, UWB and GNSS. The radios are isolated and replacing each with an open source one would be a separate thing.