I have never seen his tombstone. But his name is Lóránt in his wedding- and some family paper(s), so I assume Lóránt is the correct one.
Lóránd was probably just a typo in some researchers' publications. Not a big deal, both names are used and these 2 versions almost sound the same. Lóránd is the older, historical version and one popular University (oldest and largest) in Budapest is called Eötvös Lóránd Tudományegyetem (or: ELTE in short -
https://www.elte.hu/en/), so probably this is the more common version, that's why the error in some aviation publications.
Gabor