Thanks to the help from @BenGarrison . We were able to get this to work.
We had to submit a ticket to Meraki to have them enable the "Filter-ID RADIUS attribute with a group policy for sign-on splash" feature as referenced in this article. Once the feature is enabled, in JumpCloud, we created a new RADIUS attribute in the user group where the user group is bound to RADIUS.
The RADIUS attribute name is "Filter-ID" and the RADIUS attribute value would be the same name as the group policy that would be getting applied on those machines on the Meraki side.
The important bit here is that in JumpCloud, when setting up the RADIUS server, the IP address that you want to use is the Meraki Dashboard IP, which @BenGarrison references. We got our IP address by pinging our instance of the Meraki dashboard https://n###.meraki.com.
Once you plug in all the right settings, we could see our device authing with RADIUS on the splash page and then automatically getting assigned the group policy in Meraki!