Do we need to go that far though? Is there a case where a phone still sends data even after airplane mode is active, etc as mentioned above? What about using those called privacy OS like Graphene before we install a wallet on it? It sounds really weird tbh, unlocking and flashing your phone likely requires unlocking your firmware to install a crypto wallet, which will likely increase the risk of getting attacked with malware. I guess you don't need to think about that if you can guarantee you never connect your phone to the internet/other devices at all. At the very least, it should be better than using Ledger Live.