As well as dcloud, which Marcee1000 posted below, there's an always on devnet sandbox environment for DNA Center as well: https://developer.cisco.com/site/dnac-101/

Hmm, I'm a little confused. Are you modifying the device config locally then re-provisioning the device for DNAC to revert changes? Or are the changes just automagically reverting? DNAC shouldn't be modifying any config on the device without your inp...

Which version are you running? vManage 20.3 you activate hsec licenses on cli of the edge but after 20.5 you can apply through vManage I believe.