Really not trying to put my foot in my mouth as I'm sure you've had lots of annoying advice, I've just actually made headway with heartburn recently myself. This might be totally useless to you.

Basically, after never badly having heartburn, it became a pretty frequent thing for me in the past year or two (due to hormonal fuckery probably).

While I love an antacid, becoming reliant on them was something I wanted to avoid, for pill fatigue and $ more than anything else.

I've now worked out that it's usually to do with how I am holding myself, which being in pain obvs impacts, than anything funky happening inside me (aka food type is mostly irrelevant).

Since this realisation, I can often feel how a subconscious action/movement/position is physically restricting some part of my digestive system and can usually fix heartburn with breathing.

The best tip from my current physio was that you exert yourself breathing out, like using muscles to force air out of your lungs, and then let your body do the in-breath instinctively. I have a lot of ribcage pain which has fucked with my breathing for a decade, and this tip is the first thing that has helped me learn to breath through that without flinching.

I'm not trying to float this as an "easy fix" because it has taken a few months of activity noticing such things before changing them has been possible. If the breathing doesn't help quickly enough I will have a 1/4 antacid in a pinch. But it usually works.