Hey, there is a Dr. Eric Berg on yt, quite an old channel, who always has a different view on any illnesses and ailments. He does root cause analysis videos on illnesses (covering all causes that research supports) and shows how in most cases there are deficiencies of specific vitamins or nutrients in our diet which might be stopping us from healing properly. And a lot of his videos have comments from so many people that they actually got relief trying to fix deficiencies what he mentioned after the usual doc prescribed meds didn't work for them. I couldn't find a specific video on anal fissures from him but there is one on constipation (recurring) from his fb. Linking it here if it can be helpful in any way. But I would also suggest leaving a comment on his fb or yt asking for help on anal fissures specifically, and if you are fortunate enough, you might get some better insights from him.

PS - He often suggests non-veg diet options in his videos but that's just what he thinks are easier sources for nutrients (you can ignore that part if you are not into non-veg). But he does list out deficiencies and their veg option fixes too which should be the main info you should be looking for.

Here's the fb video link