(QR code error correction is usually enough to let you just knock out part of it and put the text right there.)
1. Have the display show a 5-digit PIN (TOTP or something that changes every minute or few)
2. Let anyone connect to your network, if they go to a browser window it will show the capture portal
3. Enter the 5-digit PIN and press "enter" and the page will show the 30-digit password so the user can copy+paste
4. User pastes password into WiFi screen and logs in
Make sure to rate-limit this endpoint to prevent random PIN attacks.