In Dante's Inferno, which group is not included in the circle of Limbo?

Well, I don't know whether you have any options, so I cannot completely answer your question. However, according to Dante, virtuous non-Christians, as well as unbaptized infants could be found in Limbo. So anyone who doesn't belong to one of these groups wouldn't be found in Dante's Limbo.

The virtuous non-Christians are people such as ancient Greek and Roman thinkers, medieval non-Christians such as Saladin, Islamic philosopher Avicenna, etc.