You're supposed to be able to add a "Debian:Next" (stretch) repo, but you have to be an "advanced" developer. What that means or how to get that status, I haven't been able to find out yet.
The MX Linux repositories
: Backports galore! If we don't have something, just ask and we'll try--we like challenges. New packages: AzPainter 2.0.4, Pale Moon 27.2.1, Liquorix kernel 4.10-2, mpv 0.24, Kodi 17.1, Ksnip 1.3.1, Mesa 13.0.6