With a little bit of search, it's possible to find lots of papers that claim to solve the issue with some kind of novel treatment. Sometimes it's training the LES or other muscle (like in the article), sometimes it's correcting some sort of dysbiosis of the gut or the esophagus (see e.g. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6469450/), etc.
It's possible that they are all true, though, and GERD can either result from multiple different causes or from a sum of different causes. If that's the case, we would need better diagnostics to figure out what is causing each individuals problems in particular.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9106553/
https://news.ycombinator.com/item?id=36059247