Professor
Yeah, if you don't want to pay for the tool specifically designed to do it, you get workarounds that are usually intensive/clunky. LM can also do it out of the box: LMConfig.
That said, what's the pain you're trying to solve? Are you trying to know which devices are on which firmware? Are you trying to catch when someone upgrades a device without you knowing? You could do a property source to get the firmware (if it's not already there) and create auto-populated group(s) on the desired firmware(s) and another where the firmware isn't what you want it to be. For that matter, regarding my previous though around building a datasource and comparing against properties, you could so something similar. Use a property source that runs only once a day to automatically generate ##intended.version##. Then run the DS more frequently comparing current to ##intended.version##. Differences would result in a value that could open an alarm.
