If memory serves correctly, do Rennes not spend quite a bit of money now and are a very decent team? Pretty sure they’ve got Doku, who looked really good in the Euros for Belgium, and a young lad Camavinga in central midfield. Although, sure the latter is touted for a big move so might not be there by the time the ties come around.
Vaguely remember there being a bit of panic from Celtic fans when they were drawn in the same Europa group.