Space opera set in OA? That’s why OA was originally created. I think most of the better stories are published in the two books in print , or some of the digital books. Chaos under heaven by xaonon , apotheosis by Kevin schillo, + a several others in the “against a diamond sky” + “after tranquility” books
Under the looking glass by Darren ryding is a good example, I think
https://www.orionsarm.com/xcms.php?r=oa-...king_glass
Here are all of the 270(?) stories+ vingettes in OA organized as a spreadsheet,
https://www.orionsarm.com/page/655
with summaries, page count, etc , which is also linked at the top of our “stories organized by author” page (which can be accessed from the front page under “read”
https://www.orionsarm.com/xcms.php?r=oa-...=by-author
I had also given an approximate rating to some of the stories as recommendations (and anyone is welcome to offer more ratings/summaries, etc
Dragons teeth, infanticide, and vagabond by Adam getchell probably count as space opera and probably have the most war descriptions
The long forgotten war by mark ryhard involves war, philosophy of war, etc , though might be more out of date canon-wise. But otherwise fine.
https://www.orionsarm.com/xcms.php?r=oa-...en_war_toc
Betrayals, & the starlark by Steve bowers
Dirty hands by Theodore Bonn
If you want non-OA space opera suggestions, I have far more possibilities.