I feel this is as close to a DS as it gets without actually buying one.

Here's a little video of me putting it together. 

Here's the component list:

• MAYFLASH Magic NS 2. https://www.amazon.com/dp/B09PT92QL1?psc=1&ref=ppx_yo2ov_dt_b_product_details
• 2x Joy Con
• Samsung Z Flip 4
• USB-C to A OTG cable (the wire part excluding ports needs to be at least 160 mm long) https://www.amazon.com/dp/B09V79YJCS?psc=1&ref=ppx_yo2ov_dt_b_product_details

Printer setup:

• Prusa MK3S+
• Prusament Galaxy Black PLA
• Infill 15%
• Prusa Slicer preset: 0.20mm QUALITY @MK3 - Supports
• Model printed vertically

CAD files are here: https://cad.onshape.com/documents/54f13c3715d8eef9adb03f30/w/02fe0c4e0a598d72cffcd496/e/80bdc376bfc54e27fd9e953d

Some notes:

The emulator I'm using is DraStic.

The snap fits for the adapter and Z Flip work by bending the case (but not too much!!).

I've put the adapter in “blue mode” which is DInput. The other modes do strange things on Android.

Some times, all the inputs seem to enter “turbo mode” (rapidly pushing inputs instead of a single on/off event). I don't know if I'm some how activating this mode or not, but clicking the button on the adapter so the Joy Cons disconnect and reconnecting again makes this go away.

As other tutorials for this adapter say, pair the right Joy Con first and then the left.