Actually I find the best option to have a cold storage and not a hardware wallet, especially a closed source one. Convenience has its price and that price is unfortunately rising.
Well, that's true. 
I gave up using my Ledger devices a long time ago, and various events from the massive data breach to them integrating a KYC debit card directly in their software have proven time and again that that was the right decision. But lots of people will continue to use hardware devices for their convenience over setting up airgapped cold storage.Using a different seed phrase will not work because in order to change the seed you have to enter wrong PIN 3 times and reset the device. The result is that the apps have to be reinstalled at the moment the device has your HD seed and this procedure is done with (drums) Ledger Live. Yeah... 
I thought there was an option in the settings to simply enter a new seed phrase, but I must be confusing it with a different hardware wallet. As I said, it's been a while since I used one.