Eat greek yogurt with active cultures.
You could make the yogurt yourself. Pick up a serving of plain, yogurt with active cultures and also half a gallon of whole milk at the grocery store. Set the yogurt aside to come up to room temperature. Now, heat the whole milk up to 180°F. Immediately remove from heat and allow it to slowly cool down to 110°F. At this point, stir in the store-bought yogurt. I also stir in 1 cup whole powdered milk because I like a rich product. It isn't necessary to do that. Pour this mixture into an insulated pot which is turned off. All this step requires is a slow wait while the cultures do their reproductive thing. I use a pre-heated, but now turned-off crock pot. After 12 hours or so, the result is YOGURT! Refridgerate half-a-cup for the next time you make yogurt.
To make greek yogurt, you take this regular stuff and drain the whey out of it. I used to use a bowl lined with handkerchiefs to do that. Now, I use a purchased container with a very small screen.
Be sure to refridgerate the yogurt.

The best probiotic in the world is made by this one real scientist in England (he cant help where he was born, right?), its called elixa. https://www.elixa-probiotic.com One reason why its so much better than others is because he has made it to actually make it into the intestine. But there are other reasons. You can do it once for 6 days, wait a month, do it again. Would work excellent with a prebiotic focused diet (using your allotted carbs on starches the good gut bugs like).
But if you dont want to spend that much, and just take one pill daily, I like a soil based probiotic. My favorite is Prescript Assist because it works for me, but right now it was recalled due to not mentioning it might have been exposed or contain some allergens like nuts and whatever. I dont care. Im still taking mine.
you might want to go read Dr Shawn Baker
he has a post about blood sugar levels and diabetes and zero carbs
very interesting, a bit of a long read but worth it.
https://www.shawn-baker.com/
https://www.shawn-baker.com/the-meat-blog/2018/5/1/k3o1g0w5ej4zydt54sxfdtbqtju7eg