[2019] the game on steam and season pass on uplay

Hi, I needed to know one thing: if I bought the game on Steam and buy, on the outside, the season pass on Uplay, can I use it or anyway or could there be problems? That is if I have the game on Steam but I buy the season pass on Uplay, can I play expansions even if I start from Steam or do I have the game on Steam? I hope I explained myself