Samsung Note 5 Unlocked Sprint/GSM (S&D)

is it usable on straight talk?

I’d say YES as Straight Talk uses AT&T GSM network IIRC…
Specs say:
UNLOCKED.

“Samsung N920P Note 5 32GB 4G LTE Smartphone Unlocked Sprint & GSM (Scratch & Dent) Compatible with Sprint; AT&T; T-Mobile”

*It should also be usable with Sprint MVNO’s…
FreedomPop/ RingPlus… but then again not due to Sprint rules…
Best to contact MVNO to verify.

*Also best to contact Straight Talk to confirm AT&T GSM is used in your area.

BTW: How much was the (refurb)Samsung N920P Note 5 being sold at?
Price is gone, sold out.