First- Presets for Lightroom (Classic and Cloudy) are always XMP files.
The reason for DNG would be for people with the 'free' version of Lightroom on their phones or ipads.
The DNG file is a raw image filetype that can have preset edits embedded within the file. The DNG file acts as a "Carrier" (like the Trojan Horse!). Lightroom-Classic users would 'Export as Original DNG' after saving the editing metadata to the file. The DNG file is now imported into Lightroom-"free" and the embedded Preset can be extracted from the DNG.
https://stayclosetravelfar.com/how-to-install-lightroom-mobile-presets/
Anyone with a subscription to the Photography Plan with Lightroom, can easily have XMP Presets Imported into Lightroom-Desktop (ie. Lightroom-Desktop on a PC/Mac) and the Presets will automatically sync to mobile devices. 'Carrier' DNGs are NOT required.
https://helpx.adobe.com/in/lightroom-cc/using/add-sync-mobile-presets.html
So I believe the answer for the OP is to Export DNG files with each Preset applied- Lightroom-Classic would be needed for this. The DNG images would be 'sold' to clients to extract the Preset in each DNG.