Is there a dust-free alternative to gravel for an indoor Petanque Court?
If this is an interior installation then no powder/gravel based playing surface will be "dust free" as the impact of the balls will create dust.  Reading up on the game, it does say that it can be played on grass.

Based on that, for an indoor game, I'd go with hard rubberized flooring (such as used in gymnasiums) topped with interior AstroTurf of a short cut.