Basel, Dynamo Kyiv, Salzburg, Olympiacos, Anderlecht, CSKA Moskva, Ludogorets, Sparta Praha, Kobenhavn, Dnipro Dnipropetrovsk, Viktoria Plzen
All clubs that are ahead of Celtic in the UEFA club coefficients. More obscure leagues have clubs regularly doing better than Celtic and other Scottish clubs in Europe these days. In terms of quality, the SPL is probably not much better than the Bosnian Premier League and other such similar leagues.