RDR is not (officially) available on PC / Steam / Steamdeck. So you’ll need to either emulate switch or 360 via Xenia. IIRC MVG had a video about RDR running under Xenia on the deck about a year ago, and it was mostly 30fps ish.
Realistically though, if you want portable play Switch. If you want to play on a TV PS4. The best way to play this right now, in the absence of PC port, is an Xbox Series X via back compat, which doesn’t really help you!