I haven’t played it yet, but from what I’ve watched and read, it seems like a totally different game within the same world (you can visit your old forts!). Looks almost like a single player game of D&D.

Update: Got the “no migrants” message for my second wave, but I DID get the Mountainhome caravan! Whatever had them scrambled before must have worked itself out.

Further migrant waves post-trading worked just fine (except for one notable refugee from my old fort, who insists she’s still in a long-dead squad…her job’s stuck at “Soldiering (no access)” or something like that, poor girl).