As title mentions above, I want to preserve my car as long as possible while keeping costs reasonable. With all recommendations saying to go by the owners manual (found here for a 2018 legacy), but for a number of things they don't seem to have intervals for a number of things only inspect or not listed at all.

Things I noticed were CVT fluid change, differential fluid change, transmission fluid change (if different from CVT?), brake fluid only mentioned for manual transmission, steering fluid flush/change, and transfer case fluid change?

There's probably other things that I haven't mentioned as I'm a very rookie budding home mechanic, but I'm thoroughly confused with what they supply. Very much unsure how I should judge when to do these maintenance items or others. Does anyone have any resources I'm missing or if it's simply forums to get these answers? Any any other big maintenance items I've missed (I am aware of things like tires and brakes but those are a lot more simple to inspect and judge when to replace I think)

Car is a 2017 Subaru Legacy 3.6R (6 cylinder, CVT, AWD of course)