Does this qualify as a "variant"? Wouldn't this fall under "thematic" games of chess?
Chess256/Random pawn chess

I think it is a variant because the pawn position is randomly generated. Thus, you don't know what position out of the possible 256 you will face ..
I don't think this qualifies as a variant, just as a peculiar way to play regular Chess. The status of Chess960 as a Chess variant is already dubious, but at least it can be argued there that you are (mostly) playing from positions that do not occur in the game tree of orthodox Chess. But here the start positions are all reachable from the standard opening position.
Chess256 or Random pawn chess is a chess variant where the pawns are randomized on 2nd and 3rd rank and black position is a mirror of white position.
Do you think it is a good variant?
I think every variant has its unique taste and improve our general chess knowledge. But do you think it is interesting like Chess960 and standard chess?
Examples of starting positions :