I wouldn’t advice on this but if for any reason Trezor Desktop app or Website gets shutdown, you can run everything locally, Trezor is fully open source. I am running trezor emulator on my linux device for testing purposes of course that wont be safe as the computer is connected to the internet but it shows you that Trezor-Firmware can be installed and run in a compatible device not necessarily the Trezor device itself. You can literally buy a small device and flash the trezor firmware on that device etc I have seen an article somewhere about the steps a guy has taken to install trezor-firmware on his own made hardware device.