xkaes,
Yes I have seen a lens board adapter for LF, and from different vendors. Don't remember who had it; ie,
an eBay seller from China, Calumet, etc...? It was advertised as being for RB [and] RZ lenses.
As stated by others, unsure how you were supposed to cock and fire the shutter, and without electrical control for the RZ lenses,
how you would obtain different speeds, other than the [dead battery] default speed of 1/400th.
I think this adapter was intended more for RB lenses, and those using a digital back on their LF cameras.
Price was high, in the $450-$550/USD range.