Hi there. I never tried this but you could turn on your ledger nano s by itself while not having it plugged into anything? Example press a button on it right now while its not plugged into anything and you can enter a pin?
What do you mean use it by using a usb charger?
As TryNinja said, it needs power... instead of connecting to the computer, you can connect a Ledger to any 5V USB power source (like a usb charger) and it will power up... if the device is uninitialised, it will commence the initialisation procedure... you don't need a computer or Ledger Live or whatever to do this. If it is initialised, you can enter your PIN and select apps that are already installed.
Note however, that you WILL still need to connect it to Ledger Live to be able to
install the coin apps like Bitcoin, BTG, and the "Recovery Check" app in the first place.
You seem like a VERY paranoid individual that seems to overthink everything... so I was simply suggesting a way for you to use the "Recovery Check" app that might help reduce the paranoia...
1. Install "Recovery Check" using Manager in Ledger Live
2. Disconnect Ledger device from computer
3. Connect Ledger device to a USB charger
4. Enter PIN
5. Select "Recovery Check" app on Ledger Device
6. Follow the instructions
The only way your seed will be compromised is if someone watches over your shoulder as you manually enter the words.
But there has been no cases where typing it in recovery key while using ledger live there was an issue right?
You don't type the recovery key into Ledger Live... you enter the recovery key on the device using the buttons to scroll and select (just like you do when you need to restore the device if you wipe it)... again, you don't have to have the device connected to a computer or Ledger Live to run the "Recovery Check" app on the device... you simply need to have the "Recovery Check" app already installed and for the device to have power (again, any 5V USB power source will work).
To the best of my knowledge, no one has ever posted a claim that their seed was stolen after using the "recovery check" app...