Fantasy recommendation:
It's not particularly "adult", but not also specifically for kids or anything (
link for discussion of adult content and appropriateness thereof), but the Dragonriders of Pern (by Anne McCaffrey and children) series has been around for a while.
It obviously has dragons, which are sentient and bond with their riders from hatching. The books start out fairly straight fantasy, but as the (massive - started publishing in 1968, most recent entry by original author's daughter was 2018) series gains more entries, some of them dig into the history of the setting where it gains more soft sci-fi elements (no starship battles or anything though). For your purposes, I recall the original books not having too much politics and not an overwhelming cast of protagonists, with action/adventure mostly being about surviving and exploring their world - the series isn't about war. It's been a long time since I read these and I only read the earlier ones, so I could be somewhat mistaken in the ratio of action/politics, but that is what I can recall.
To get into it, I'd go with either the original trilogy:
Dragonflight/
Dragonquest/
The White Dragon, or the Harper Hall trilogy:
Dragonhall/
Dragonsinger/
Dragondrums. Apparently
The White Dragon incorporates some of the characters in the Harper Hall trilogy, and the author recommended that people read those three before
The White Dragon, but I don't think that sticking with one trilogy would make things too confusing.
If you do like those, the later books are a mixture of direct sequels to each other and standalone novels, and tend to bounce around in the timeline of the setting - the series isn't a single long tale to be read in one specific order only.
Sci-fi "recommendation":
The Honor Harrington (by David Weber) series is 14 novels, with additional series/anthologies in the "Honorverse" by Weber and other others. The series is about an officer who goes from commanding one small starship (a frigate or something) to an admiral. In high school I tried to pick this up, probably somewhere in the middle of the series and got through about one and a quarter books before getting bored due to what I described at the time as "too much politics" (enjoyed the first one I read).
In my adulthood I have since read and enjoyed GoT, and also have read a (possibly abridged) graphic novel of the first Honor Harrington book and found it to have plenty of action/adventure (spending sufficient time on battle specifics) and not much politics. As a result, I am not sure you'd actually like this but it may be worth finding out more information on. I'd probably tolerate it a lot more now than I did back in high school myself.
Addendum:
Should you decide that dragons aren't actually all that important, I can recommend a handful of things that are definitely adult due to the violence/matter of fact brutality in the setting, have lots of well explained action, and not much politics (protagonists are small players in a big world, so politics is something that largely happens to them, not something they take part in).