Yeah, the manga ends abruptly, sadly this is more usual than it should be in the manga industry, as soon as a series doesn't meet the popularity/sales they want they just self the series, sometimes as is the case here the author is given a few more issues to try and wrap up the story the best they can but normally doesn't work great as it is the case here. Some people say that this was the intended ending but I find hard hard to believe that.
The Netflix anime likewise is half finished in that it tackle an "finish" entire arc but let many things half way (the anime covers roughly 2/3 on the manga iirc). Either way I think is a very interesting series to watch even if only for the world building.. there's plenty of mecha stuff but I don't think is the main focus of the series. If you have access to it I'll recommend watch the first 2 episodes (or even the first one). If you're not hooked by then, then it won't get any better for you.