TL;DR: download the zip file from here (search rehid_w_virtual_sliders on github) and unzip it to your sd card root. Make sure you have FIRM patching in Luma3ds settings. Use START+L/R to adjust volume, SELECT+L/R to adjust 3D. Does not work under DS (+ GBA?) mode.
You don't need rehidhelper...
I may try the new ram site, and download more RAM to my Switch. Not sure if ddr3 is the right ram
for it tho. Edit- no it uses floppy Ram, just like @AncientBoi