I’m looking for information on significant Wookiee populations beyond their home world. I’m guessing they aren’t really an expansionist species, but they might have found a couple garden spots to settle down.
Wookiee Diaspora and Colonies?
There doesn't seem to be any information. Not in canon and not in Legends.
But I think it's safe to say that whatever colonies they had (if any) were easy pickings for the Empire and other slavers.
Off the top of my head, the Wookiees had colonized the moon Alaris Prime in the Kashyyyk system.
These are the only two which I am aware of...
In addition to the above mentioned, Wookiees (in Legends at least) have been spacefaring for a few thousand years. They've likely colonized a bunch of planets that are just unnamed because in a galaxy of billions upon billions of worlds, all the authors, screenwriters and games in existence won't be able to name them all. If you need a Wookiee colony, just make up some unpronounceable name with lots of R's, O's and Y's and place it in the Mytrantor or surrounding sectors.