These are some rough steps for setting up Windows dual-boot on the Steam Deck. Please note that this may or may not work, since I didn't follow this exact path and did a lot of experimentation to land on these recommendations.
Things you need:
- A decent chunk of time (1-2 hours if things go smoothly) set aside to set this up, doesn't have to be all in one go
- Enough free space (at least 30GB) on your Steam Deck internal drive for a Windows install plus games. Note that if you just follow this first set of steps (eg. if you don't want to buy a Paragon Linux Filesystem for Windows license) you won't be able to use your SD card for Windows game storage.
- 1-2 USB sticks (depends on if you want to burn Windows to USB beforehand or after you do the partitioning)
- A keyboard, although you might be able to get away without it since Windows Setup has pretty good on screen keyboard support w/ the touchscreen
- USB C to USB A adapter if your USBs or keyboard are USB A
- Some knowledge of partitioning. There are