The F-1 stamp is still valid and you can travel on it, but it certainly isn't intended for being abroad for 6 months.
I say what I said above because it happened to a handful of candidates I have seen over the years, from red flag countries especially, where they have left the U.S. on STEM OPT, and stayed outside the US for an extended period of time and tried to return on their F-1 stamps. They were denied entry at the border because they are no longer students, therefore entry on the F-1 was denied. Similarly, the EAD card, where they have STEM OPT, is likely not authorized for re-entry.
It would be risky, and I have a hard time imagining that border patrol will authorize entry.