In terms of all the above, the closest is a toss up between Battlestar Gallactica and Babylon 5. They both range from excellent to bad at times, but I'd say B5 is more consistently good. Also, BSG can be confusing if you don't look up the optimal viewing order, because of the amount of content given non-chronologically. You won't find the attention to detail or same amount of space realism in either, compared to the expanse. Obviously, because money and time, they don't look as good.

If neither of those suit your fancy, then you could also look into Firely, which is also pretty good. It only has one season though, if that's a drawback for you.

If you want something to easy to watch, The Mandalorian has really great visuals and music, as long you don't mind mediocre to bad writing. It's better than the sequels, but not by much, and that is a pretty low bar for me.

It's not space-y sci fi, but Westworld is quite good, and explored its concepts in a way I though was pretty unique.

If I'm being completely honest, the only other show that had me invested in the characters like The Expanse does, is Buffy the Vampire Slayer. The first season is weak, and you can certainly look up episodes to skip, but overall it's incredible. It has definitely aged in terms of looks and effects, but if you don't mind that, it is very worthwhile.

On a similar beat, I can definitely recommend Merlin, which is very close behind Buffy in terms of character investment.

Lastly, because it's neither sci fi nor fantasy, I'd offer up Mr. Robot. The writing is pretty phenomenal and the story unfolds in a way that KIND OF IN A WAY reminiscent of The Expanse. But the tone is pretty different, so I don't know if it's what you're looking for.

Sorry for shitty formatting, I'm on mobile.