I'm looking for a good sci fi series to get lost in. In addition to The Expanse I've liked shows like Dark and The Rain. Doesn't have to be set in space but it's always a plus.
Not the same kind of sci-fi, but it's great and well worth watching.You may like For All Mankind on Apple+. Alternate history show about the US/Russia space race.
Unfortunately there's nothing similar to it because it's the only show that does politics and conspiracy in a grounded space sci fi setting.
For All Mankind comes close, while Expanse is a political thriller set around the ramifications of realistic space colonisation (with some fantasy ala Protomoleculez Ring Gates, Ring Builder Civilisation etc) in far future. For All Mankind is a character drama set around realistic space colonisation (with little to no fantasy elements) set in our past. But because it's set in the past, it's low tech.
You may be interested in The Foundation that's coming out in Apple TV+. It's a bit more fantastical and isn't about space travel, but it's basically going to be a socio political drama about an unimaginably advanced and large human society set in the far far future (50,000 years from now) that's at the brink of collapse.
I just started with Altered Carbon and it gives me similar vibes.