I just hope that his goal is not to create a seed with Trezor, and then use it for desktop/mobile wallets.
Me neither. That's why I asked the user what they are planning to do. Those new to hardware wallets may believe that connecting a hardware and software wallet entails importing the seed into the latter. That's not the way that connection is supposed to be established. The seed and private keys must remain on the device. If the hardware wallet breaks, get a new one. Don't get scared or uncomfortable and input your seed into hot wallets just to see if it will work. That just increases the possibility of compromising the safety of your coins.