NGC 7331

You're just over an hour of integration at f/12.7 --not bad! Maybe try making your background not so black--not saying you're clipping it, but I think it will help bring out some of the fainter detail. And maybe less denoising, which I imagine you did use, since you only have the integration time you do...that will help preserve some of the fainter detail too. I am surprised there doesn't seem to be as much star colour or colour in the core of the galaxy as I would expect--you could probably push the Arcsinhstretch a bit more-- ? try several small stretches to see if you can get colour showing, then if you need more stretch, go to straight histogram manipulation. Not sure what Siril offers for sharpening, but you could just try a bit of unsharp masking as a trial too. 

Save your calibrated frames (to save having to reprocess them later, if you have the storage space) and just add another hour or two to this and compare. Better yet add another 3 or 4 hours! 

Thanks for the suggestions!  I've tried a few time to squeeze more out of it, but it seems like the data just aren't there to differentiate the faint outer regions from background noise.  Needs a lot more cowbell, for sure.

To a large degree, my difficulties stem from my cheap mount.  Tracking is very erratic, and less than half my subs are stackable.  A good evening for me would be 30-40 usable subs over the course of 3-4 hours.  This image is the result of 8 different nights of work.  Getting "another 3 or 4 hours" would be a monumental task.

Frankly, given my limitations, I'm fairly happy with getting a smudgy picture of something that is 40 million light-years away!

I'm on the cusp of buying a new mount.  Thinking about an iOptron GEM-28.  If I can get a reliable succession of reasonably well-tracked 30-60 second subs, that 3-4 more hours might well be do-able.

Thanks for looking!  I loved your shot!