Some recent evidence points to the Earth’s magnetic field playing a part in preferentially selecting right-handed chirality in RNA precursors. This work is not complete though as not every nucleotide can be made from this process yet, but it is so far, the best explanation available as to why genetic material and amino acids are exclusively R and L (respectively) oriented.
I also remain sceptical. I don’t think there necessarily must be some mechanism to break the symmetry, it could have just been a cosmic coin flip. This is different than something like matter/antimatter in which there needs to be some underlying physical process introducing a bias.