To enable Captive portals for MacOS devices, as outlined in this Apple Support page, it is necessary to have MDM to set the ProxyCaptiveLoginAllowed value to True instead of its default setting of False (Disabled).

Many MDM providers, such as Securly MDM, Mosyle MDM, and Filewave, have this feature integrated into their profiles, which typically involves a simple toggle. However, I am uncertain if Jamf offers this capability for MacOS, so we may need to reach out to JAMF Support for clarification. If ProxyCaptiveLoginAllowed is not available in your MDM, you can utilize Apple Configurator 2 software or the free tool iMazing to create a custom Proxy profile, and then use MDM pro to deploy that mobile.config profile to your devices.

Please check the attached video HERE where I show an example of a Proxy profile created in Apple Configurator 2.

Additionally, we have received feedback from several JAMF schools indicating that the method of pushing the MDM Profile is significant: if it is pushed at the System level (device level), Captive portals will not function with any Proxy settings. However, Captive portals work effectively when applied at the “user level.” (please refer to the image below)

How to enable captive portals for MacOS devices