I think that porting Firefly to GTX/RTX-based computing is project by itself because, if I've understood correctly,  not everything's possible using a GPU.
The "Branched Path Tracing" option is a good example of what is actually not possible, as a GPU's instructions set is rather small, compared to common CPU's

𝒫𝒽𝓎𝓁

---

(っ◔◡◔)っ

👿 Win11 on i9-13900K@5GHz, 64GB, RoG Strix B760F Gamng, Asus Tuf Gaming RTX 4070 OC Edition, 1 TB SSD, 6+4+8TB HD
👿 Mac Mini M2, Sequoia 15.2, 16GB, 500GB SSD
👿 Nas 10TB
👿 Poser 13 and soon 14 ❤️