“Experts” are generally offering advice about a *colonic* microbiome. Even the most audacious among them wouldn’t claim expertise in maintaining a healthy J-pouch microbiome. You’ll do better, I think, if you try various things and pay attention to what makes you feel best.

I can eat sauerkraut, tempeh, Greek yogurt and even kimchee with no problems. Google a list of fermented foods and experiment to see what you can eat without discomfort (gas). Go slow. Too much fermented foods at once might cause gas until your stomach and j pouch gets used to new foods. 

Quick answer is cook things and chew till it's liquid!  My jpouch is now in permanent retirement, but since I have no colon, I think we're in the same boat in regard to your question. I had a jpouch for 30 years that was pretty manageable although had to take Cipro (no others) almost the entire time.  Last few years fistulas and anal canal narrowing caused lots of problems and I got a permanent ileo.  7 mos out now and I'm the healthiest I've ever been.  My blood work is normal and I'm not on meds and don't have to worry about where the bathrooms are.  Right after the surgery I started eating anything - ie gluten, sugar, vegetable oils ..  Got some serious skin issues said to be Crohns related and my GI wanted to put me on Humira. I realized I'd be better off sticking to what for me is loosely AIP Paleo with a big focus on my microbiome. Typical meals- pastured eggs/salmon/olive oil, soaked/sprouted nut butter/dark chocolate, Instant Pot ground beef stew w/garlic/onion powder, lots of fish, well baked carrots/olive oil, casein A2 butter, sourdough bread, strawberries (heated in micro to make sure no blockage issues) with yoghurt/cinnamon, live sauerkraut juice- sometimes a couple bites actual kraut well chewed.  I also supplement with Natren probiotic powders and acacia fiber. There wasn't anything out there about diet 30 years ago when I got diagnosed w UC/Crohns and within 6 mos had my colon out/jpouch, so I do sometimes wonder if I could have saved my colon. Having had my jpouch for decades, I think the main issue became mechanical and diet really couldn't prevent the final surgery for an ileo. I always had a really narrow connection between the pouch and anal canal that I think was ultimately susceptible to infection. Overall wherever someone is in their journey, I strongly believe diet and managing your microbiome makes a huge difference.  I now do GI Map tests to monitor my microbiome every 3-4 mos (done 2 so far post surgery) and use natural antibiotics (like wild oregano oil or olive leaf) if I need to to keep things in check. Good luck to everyone.  I know it can get dark at times with these conditions, but I believe the body can do remarkable things to heal. 

Can you share more about the GI Map test?  How do you get that done and who knows how to read the results?

Here is the link https://www.diagnosticsolutionslab.com/tests/gi-map which gives you a lot of info.  I have ordered it through my health coach but I think any doctor can order, or you could ask the site for a referral.  They have a PDF on the site that goes through all the various bacteria, viruses, etc that they test for and what it means.