You can create Smart Groups from application versions natively in the Jamf Pro UI. Use criteria Application Title and Application Version. The latter criteria lets you use a regex pattern instead of anything absolute, which should give you the ability to look for versions below a certain number. For example, say you wanted to capture any Macs with a Citrix Files version below 20.x, something like this may work. It kind of depends on the versioning scheme for Citrix Files, which I don't use myself, so I don't know how it's versioned.
1[0-9].[0-9]
That would capture anything starting with a 1 and followed by any number between 0 and 9, and then any other number following the period. The regex might have to be modified a little depending on things.
I would at least give that a try first.