I've looked into the state of research on font legibility many times over the years, and this time I came across this thorough thesis from one Dr Liz Broadbent[0] (who sadly passed away recently).

It includes a great rundown of all the studies that have been done regarding font legibility and dyslexia. I remain completely unconvinced that any of these fonts offer a measurable improvement in readability over, say, Arial.

A big problem I see again and again is that the sizes compared are not fair - the author notes that spacing likely has a large effect on results and that different studies have tried to account for this in different ways. In her own study the author compares 16pt Arial with 15pt OpenDyslexic in an attempt to match the x-height. But in terms of how much space on a page a given text takes up, 15pt OpenDyslexic is actually equivalent to 25pt Arial! On page 154, a study participant even points out that it's clearer to read because it's bigger.

But overall I'm just glad funding is being directed to serious research on this topic.

[0] https://discovery.ucl.ac.uk/id/eprint/10173561/2/L.Broadbent...