Can I run Ornith-1.5-35B-A3B-GGUF on an RTX 4090?

No

Even its smallest file (Q4_K_M, 21.7 GB) is more than an RTX 4090 can hold (21.6 GB usable): it needs 2 of them.

Files and context on RTX 4090

Each file of Ornith-1.5-35B-A3B-GGUF (and of GGUF versions the site has analyzed), and how much context fits next to it, with the context cache in 16-bit or 8-bit.

Ornith-1.5-35B-A3B-GGUF on other hardware

Popular models that run on RTX 4090

Assumes 90% of the card's memory is usable and at least 4K tokens of context for one conversation, with the context cache in 16-bit unless noted. Fits leaves at least 20% of that memory for context; Tight leaves less.