This looks like the only call that returns app data, you'd need to try it against a test device to see if the return data gives what you are looking for...
https://developer.cisco.com/meraki/api-v1/#!get-network-sm-device-softwares
You will need to find your organization ID, you can find it with...
https://developer.cisco.com/meraki/api-v1/#!get-organizations
Also you need the network ID of a system manager network, use this to find all networks and choose an SM one...
https://developer.cisco.com/meraki/api-v1/#!get-organization-networks
To create a script to automate things, the loop would be...
get all networks in the org with...
https://developer.cisco.com/meraki/api-v1/#!get-organization-networks
iterate through that list, testing the productTypes element
for each network that is a system manager network, run the get-network-sm-device-softwares call to get the device data
I recommend using the Python API library as it does a lot of the low level stuff for you...
https://pypi.org/project/meraki/
