Assuming you mean legally, the best options are Paramount+ (or whichever service it’s on outside the US) or on Blu-ray. None of the television series are available in 4K to my knowledge, but the movies are.

I don’t remember exactly what lead up to it, but I ended up watching reruns of Voyager with my dad every day back when Spike TV was still a thing. I think that really improved my relationship with him.

I use Strawberry for mine.