The trick is to use whatever that is built into the system you are using. On iOS I use the Shortcuts app to create an action to generate QR codes. On desktop I just use Chrome's built-in QR code generator right from the address bar.
Assuming you already trust your OS and your browser, this means you do not need to trust any additional party for this simple task.
Assuming you already trust your OS and your browser, this means you do not need to trust any additional party for this simple task.