After my last post, the advice given, and some more research, I made some jalapeño blackberry jam. It's currently sitting on a towel for the required 24 hours to set up before it goes in the fridge/freezer.
Tasting off the spoon, it's pretty good. Mostly blackberry with a hint of heat. I won't know until it's ready, but I suspect I might not really care for the "raw" texture of the jalapeños. If I make it again, I'll probably try cooking the jalapeños some (with part of the water used to cook down the blackberries).
I'm not sure if I'm allowed to/required to post the recipe I used. More than happy to!
From my understanding, freezer jams don't really have to follow the same "safe" guidelines that shelf stable canned goods do. If I'm wrong on that, please give some guidance.
I really appreciate all the good this community does. I've grown so much in my canning (or freezing/preserving) journey. Thank you all so much!