Rendering SDR out from DaVinci Resolve
In the Deliver window on Resolve, when exporting an IMF, the render button must be set to Single clip.
Rendering with iCMU
Resolve can render out a mapped version by using Dolby Vision metadata ONLY if you're using iCMU. Temporally switch to iCMU if you are currently using eCMU.
Choose 'Single Clip' instead of any other templates associated with 'Individual Clips'. Resolve will not apply the Dolby Vision mapping when rendering individual clips, out of version 16.2.