Louis has never said he's straight or that he's "not gay or bisexual", as far as I know. I am often criticized for reminding people that bisexuality exists but I feel like it's an appropriate answer in 2021 to assume that he's straight because he has a girlfriend.
Last year in an interview, Louis was very clear in repeating that he had a girlfriend (
»Wenn man selbst keine Wahrheiten mehr hat, kann man diese auch nicht spielen.«), but who knows what their relationship is or whether that means he has never had sex with men or interest in men. Men have been doing the expected thing socially for years and having sex on the side with men and women have done similar things with women (I speak from experience). Louis also described himself as rather unused to dealing with emotions. He's 23.
Now that Jannik has come out, we can go back to what was said before. Jannik was almost certainly the one the director referenced that had sexual experience with guys. Louis - who was barely 18 when Centre of My World started filming - was the one who was uncomfortable at first being intimate with a guy. He has clearly gotten over it on film. But we have no idea what he does in private or whether he's bi-curious, bisexual, etc., or "straight", or that he himself has hangups about being in a relationship with a guy or what his relationship with anyone. He keeps the girlfriend quite private.
Louis is also a young actor, short of stature and unlikely to get certain roles because of it and who knows what as he ages. But consider this: If his co-star, who was in a relationship and but very private and deciding not to live more openly on social media, why should Louis? He's projecting the image he wants to protect and keeping the rest private.
