This video shows you how to set up the Svideo adapter designed by Mike Simone for the MiSTer FPGA.

[MiSTer.ini settings]
vga_mode=svideo ; supported modes: rgb, ypbpr, svideo, cvbs. rgb is default.
ntsc_mode=0 ; Only for S-Video and CVBS vga_mode. 0 - normal NTSC, 1 - PAL-60, 2 - PAL-M.
composite_sync=1 ; set to 1 for composite sync on HSync signal of VGA output.

To see a list of vendors selling the adapter checkout this RetroRGB article: https://www.retrorgb.com/mister-s-vid...