There are a fair amount of handwired ones, prototypes, higher key count boards or 2 key thumbs as options for farther away thumb clusters as well. You could also try to get more than 3 thumb keys and not use the ones too close to your thumb.
Might be worth looking through if you haven't already:
Honestly could swear I had seen more, but when I checked 3w6, waterfowl, or several others it was just really long thumb clusters. Not actually lower down on the board away from the alphas sadly.