unfortunately, upstream mpv is extremely hostile to NetBSD. actually, if you asked some users of Linux and other BSDs, upstream mpv is extremely hostile to everything.
i recommend sdl video outputs. if this and opengl don't work something needs fixing system wide, falling back to x11 is indicative of a problem. ffplay (another player) should also be extremely reliable. my impression is that the "2014" driver should no longer be needed - at some point newer NetBSD automatically uses an uxa AccelMethod on older intel gpus. but even software gl with llvmpipe and wsfb should be better than broken-mess-drivers.
