Hi Antonio,
Hope you are doing well,
You would be able to open the web apps in kiosk mode by making use of the Google Chrome browser. You can have this set from Policy > Kiosk lockdown > Android > Website kiosk settings > Another browser. From here, you would be able to add the Google Chrome app. Please do note that this app should be installed on the device.
Since you would like to have the Chrome app hidden from the users, you may have it added as a background app from Policy > Kiosk lockdown > Android > Background apps. By doing so, the users would not be able to run this app directly, however, they would be able to run the web apps using the Google Chrome browser. Here is a detailed help doc to guide you through this https://www.hexnode.com/mobile-device-management/help/how-to-set-up-a-website-kiosk-with-hexnode-mdm/
In addition to this, if the devices are enrolled under Android Enterprise and the Chrome app provides the configuration to whitelist URLs, disable saving browsing history, blocking third-party cookies etc, you would be able to have this configuration deployed to the devices from Policy > Android > App configurations. This way, the users would be able to access the web app alone.
Please do ensure that the app has been added as managed Google app first from Apps > Add apps > Managed Google apps. Here is a detailed help doc regarding this feature https://www.hexnode.com/mobile-device-management/help/set-up-permissions-and-configurations-for-an-app-using-hexnode-mdm/
Stay safe and have a great day!
Cheers!
Jeff Black
Hexnode MDM