Is there a dummy fill flow for sky130nm? Which commercial / opensource tool has the automated fill flow?

Magic does. There is a script for this in open_pdks, and as @Anish mentioned, it is also in the caravel repository under scripts/. The one in the caravel repo is specific to the caravel chip projects; the one in open_pdks is a bit more general-purpose. But I updated the one in the caravel project recently to run multi-threaded and have not transferred that update to the one in open_pdks.

Okay thanks. How about commercial tools? Do we have cadence script (presumably for PVS) as well?

openroad also has a fill capability. Generally commercial tool scripts can't be shared due to NDAs.

@Tim Edwards Where can I find the magic script in open_pdk which does general purpose fill?