i haven't watched a series in a looong time

what's a good one to start?

If you like the Star Wars universe, some of the spin-off series are pretty entertaining (and extremely well-made.) They're all on Disney+.

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i've only seen the first (fourth?) one, big cultural blind spot for me

You could definitely watch the spin-offs without watching the movies, but just miss a bit of context. Something completely different since you're not a big Star Wars fan: Last Man on Earth is a funny series for Will Forte fans. Lots of hilarious cameos in it also. Good luck finding a great series you like!