It’s not very hard to find the information you seek in this forum so I’m not sure where you are reading that . The AM6B+ supports DV FEL. There are other devices too that supports it.
See YadaYada’s excellent post here:
CE-NG Dolby Vision (+FEL) for DV-licensed SOCs (s905x2, s922x/z, s905x4) - Development / Development & Testing - CoreELEC Forums