How to convert Dolby Vision HDR to HDR10+?
Sadly no, not without expensive specialist broadcast processing hardware.
From the Reddit link,

Dolby Vision is 100% proprietary. There is no incentive at all for
Dolby to convert anything to HDR10+ to help out Samsung users (and
pre-2019 Panasonics) when the only reason HDR10+ exists is because
Samsung didn’t want to pay Dolby for the license.
Dolby Vision is simply an enhancement layer on top of HDR10 which is
the base layer. There are a couple types of DV layers. The MEL
(minimum enhancement layer) and the FEL (full enhancement layer) which
reconstructs the original 12-bit signal. The FEL is what gives DV a
large advantage over HDR10 and HDR10+.
Page 12:
https://www.dolby.com/us/en/technologies/dolby-vision/dolby-vision-for-creative-professionals/dolby-vision-uhd-bluray-authoring-workflow.pdf