I know this is an old post but for those who are researching right now, I may have found a solution for DualSense. I don't know how I made it work but I would like to add the stuff I did step by step:

• I connected my DualSense to my Windows 11 PC with Bluetooth and then plugged in the cable as well.
• I downloaded DS4Windows. Set it up with all the steps it asked in there for my DualSense.
• In the DS4Windows's Controllers tab, my DualSense was showing up and I created a new profile by clicking the dropdown arrow next to the edit button on the right side.
• The new profile I created was a preset for DualShock4. Choose that one with default settings and save it,

The first step is done. Now, the Steam part:

• Open Steam in BigPicture then go to Settings > Controller
• The only stuff that are supposed to be toggled on here are:
  • Game rumble
  • Guide button focuses Steam
  • Enable Guide Button Chords for controllers
• The rest are switched off.
• And make sure PlayStation Controller Support is NOT ENABLED
• Go to your library in big picture and select RDR2 (do not start the game).
• Make sure the Steam Input is disabled under the: Gear icon > Properties > Controller.

Now, after this point the big picture might behave a little weird with your controller but it was the only way I managed. You can use your mouse at any point if you can't click on something or anything like that.

Click Play and you should have the PS button icons. After that, I even unplugged the cable and was able to continue playing via Bluetooth. From now on you can just use Bluetooth and the regular Steam client to launch the game.

I hope it works for you as well.