RenoDX is a modding toolkit that, among other things, allows reconfiguring (certain) games to output true HDR.
XXMI is a modding platform focused specifically on efficiently replacing game visuals.
ReShade is a modding toolkit for developing post-processing graphics effects as well as an injector for said effects.
RenoDX relies on ReShade to work, and XXMI helps inject ReShade as well as uniformly manage modded games.
To achieve true HDR in any given game you will need a ReShade add-on that uses RenoDX's capabilities to do just that, designed specifically for that game: