If you are talking about cross flashing that is typically blocked by Nvidia. On top of that, the Dell OEM has design decisions made that would make it not compatible with certain bios features like under-volting or power requirements.
Has anyone tried a Bios flash on their 3090 GPU, if so which Bios did you use to flash? It's an Alienware card, always had what's considered low scores for a 3090 in 3DMark, around 18800 - 19200, which is 3080 territory. My actual temps on this card are very good after modding, so it's not thermal issues. 
Aurora R16, RTX 3090 Bios Flash