From what I saw on their Patreon, they wanted to sell it on Steam, but due to Steam's strange content moderation regarding Adult Games it got stuck in review hell. They started doing some contract work and working on a side project in the mean time. To top it off, the Russians cutting off the power supply in Ukrainian cities probably also isn't helping with progress.
I think the dev still wants to do the DLC, but wants to make sure he is able to actually sell his game without having to rework everything for the steam version.