If you use DeployGate on iPadOS, you would not be able to install the app with the default settings, as an error message will be displayed like below.

"The iOS version could not be obtained because the page is displayed using the desktop version of the website. "

Please follow the instruction as below.

Open the Settings app and turn off “Safari → Request Desktop Website → All Websites”.
Return to Safari and reload the DeployGate page.