I did get a brief period in winter 2020/21 (2 months approx.) when I had heartburn. That was about 10 months after my IBS D symptoms began in the Spring 2020.
I tried DGL licorice and took it exactly as suggested. I have forgotten the exact amount now, but it was a fairly small scoop of it. I had a special tiny spoon. That was 3 times a day about 30 minutes before meals. I only eat twice a day, but I also took one scoop before bed.
But I was also backing that up with home made herbal bitters, elevating the head of my bed about 8 inches and sleeping every night that way, plus I also chewed small amounts of calcium citrate tablets for that awful unstable sensation in the lower esophageal sphincter.
I also more or less gave up drinks with caffeine as caffeine definitely irritated my stomach. I could not bear to even drink green tea. I really missed my morning coffee as it's made with a special ground coffee and there's no decaf of that brand. I hate instant decaf coffee!
So I don't know if all those things put together helped. Maybe they did, because after 2 months the upper stomach symptoms disappeared, and haven't returned yet.
My IBS D did continue though. They are not as bad as some people get, and I have many periods when I'm close to "normal" but they are still there and didn't disappear also.
I did love the taste of DGL licorice, and it was good to know that taking that wouldn't have an impact on my blood pressure, or cause any other side effects from long term use as "entire" licorice can sometimes cause.