This can be anything from Hyperspace in Star Wars, Warp Drive in Star Trek, travel through the Warp in Warhammer 40k or anything else.
I’ve always liked “slow” FTL travel, where going a few light-years still takes a few days or so. I also really like travel through an alternate dimension like in 40k, Event Horizon, Witchspace in Elite Dangerous.
I wanna know your favorite versions, or do you prefer stories that obey the laws of known physics, like the Expanse or Rimworld?
One of the more interesting (and creepy, and appalling!) FTL systems I remember is from Scalzi’s The God Engines. Way back in the day The Lord subjugated all other gods, and these gods are now prisoners of human ships, and responsible for moving them through the stars.
I’m fuzzy on the details, but I remember engineering was replaced by a priest caste, and their prayers kept most ship systems running (this Lord is a very active deity!) I also remember that the ship-gods can be very recalcitrant - I think the book opens with the captian having to whip the ship’s god into compliance.