Hey there!
Steam is still learning about Afterdream, so there's no Steam Deck -badge visible yet. However, I'm happy to inform you that Afterdream plays beautifully on my Steam Deck, running butter smooth 60 frames per second without dropping frames.
Only minor difference I could spot from the native PC version is that sometimes subtitles outline is one pixel off. It doesn't affect readibility, though!
That said, you can expect Afterdream to work out of the box. But in case of any problems, please try restarting your Steam Deck first!
Thank you very much for your support. I hope you'll enjoy Afterdream as much as I enjoyed creating it! :)
Jesse