Correct me if I'm wrong — if we use an open source Bitcoin wallet but after getting the address and seed phrase stored in a waterproof and fireproof place or not damaged by water and fire, the wallet is uninstalled from the mobile device, I think that's one way to use it well. Is it right?
Sounds like you're trying to generate an air-gapped wallet/cold wallet but using a mobile phone to generate the seed, is that right? I'd rather use another device, like a freshly installed/disconnected computer or a live OS to do that instead of a mobile phone. Unless you disconnect your phone, reflash the OS/ROM, and then destroy it I don't think I can feel safe. Might as well buy an open source HW. CMIIW.