Sumo Logic doesn't have specific integration with Ubiquiti Unifi-controller but the most common way to push any sort of network or firewall logs is using Syslog and for that typically you need a local collector with a Syslog listener as a source.
Here's a link on how to install a collector on Linux: Install a Collector on Linux
Setting up a Syslog source is fairly simply - define TCP or UDP and a port number to create a Syslog listener source. For more info: Syslog Source
There is a very good article that can be seen from below link on the Ubiquity networks community site that matches exactly this requirement: