using a Fedora-based sys-usb VM and a Whonix WS-based application VM:
navigate to the Trezor instructions page and read them. They are more frequently updated than this document.
in dom0: sudo vim /etc/qubes-rpc/policy/trezord-service add this line: $anyvm $anyvm allow,user=trezord,target=sys-usb replace sys-usb with disp-sys-usb if you are using a disposable sys-usb
in the sys-usb VM, or for disp-sys-usb, the VM on which it is based (in both cases, assumed to use a fedora-3x template): sudo mkdir /usr/local/etc/qubes-rpc sudo vim /usr/local/etc/qubes-rpc/trezord-service and add this line to trezord-service: socat - TCP:localhost:21325
in the whonix-based application VM: pip3 install --user trezor sudo vim /rw/config/rc.local add this line (note the "&" at the end): socat TCP-LISTEN:21325,fork EXEC:"qrexec-client-vm sys-usb trezord-service" &
in the fedora-3x template: sudo dnf install trezor-common
download the bridge RPM from https://wallet.trezor.io/#/bridge and remember to verify it!
copy to fedora-3x
in fedora-3x sudo rpm -i /path/to/trezor.rpm