One of the subject genes is called MTHFR. It reduces the methylation of Folic acid by ~30-40%, depending on which paper you read. Tons of people have this. It was this AND a gluten sensitivity which resulted in me having actually low levels of usable folate.
To find out if you have this go to this link: https://you.23andme.com/tools/data/?query=MTHFR. You can enter various other SNPs there if you find any of interest.
You can download your DNA there and enter it in another site that can tell you the other genes that could affect this sort of thing.
There are other things that could affect other people in unique ways so of course this isn't the only one.
What I did is ask Claude "why would eating meat make me feel dramatically better" and it told me about these genes. And then I went to 23andme where you can see individual SNPs and then I searched for other related SNPs.
I also seem to have non-Celiac gluten sensitivity which affects my absorption of Folate (and other things if I have recently eaten gluten which was almost always until recently) which is why this was a problem for me. And zero doctors or companies have ever developed a test for this or even take it seriously, including allergists and immunologists that I saw.