Bypassing ngrok warning page in a browser and console

Question

I was designing a website and would like to host it using ngrok, which I want my clients to scan a QR code to enter it, however the browser warning might give the user a bad experience and might leak my IP address.

I looked up in some other pages in stackoverflow, but they only said to add the header ngrok-skip-browser-warning: true. So I added a header using --request-header-add 'ngrok-skip-browser-warning:true' in the console. The following is my command ngrok http 8000 --request-header-add 'ngrok-skip-browser-warning: true' and is tells me

ERROR:  You must specify a single argument: a port or address to tunnel to.
ERROR:  You specified 2 arguments: [8000 true']
ERROR:  For example, to expose port 80, run 'ngrok http 80'.

and if I delete the space like ngrok http 8000 --request-header-add 'ngrok-skip-browser-warning:true', the tunnel opened, but the warning still didn't disappear. I've tried Shift+F5 to force reload. And I'm using a free plan so I can't add edge request header like one answer showed. can't add header

Also I tried using a config file to save and run the setting as follow

version: "2"
authtoken: 2RgBb4AnFQ0Ovss1Xec4qeHV7ve_7B1E2EcpcaGssKiW8soPJ
tunnels:
  example:
    proto: http
    addr: 8000
    request_header:
      add: ["ngrok-skip-browser-warning: true"]
    domain: badger-glad-steadily.ngrok-free.app

It did start, but showed the warning.

As I mensioned before, bypassing it is for my clients, so I won't be likely to change header in the original request made. Iwould like to know how could I accomplish bypassing.Thanks.