What's the best speed people have gotten on 4090s?
Flash attention works with GPT-OSS + llama.cpp (tested on 1d72c8418) and other Blackwell card (RTX Pro 6000) so I think it should work on 5090 as well, it's the same architecture after all.
For home use, Gemma27B QAT is king. Its almost as good as Deepseek R1
The 120B is running at 20 tokens/sec on my 5060Ti 16GB with 64GB of system ram. Now personally I find 20 tokens/sec quite usable, but for some maybe it's not enough.