Use 4 consumer grade 4090 then. It would be much cheaper and better in almost every aspect. Also even with this, forget about training foundational models. Meta spent 82k GPU hours on the smallest llama and 1M hours on largest.
Go with 2x 3090s instead. 4000 series doesn't support SLI, so you're stuck with the max of whatever one card you get.
If I remember correctly the NVLINK adds 100GB/s (where PCIE 4.0 is 64GB/s). Is it really worth getting 3090 performance (roughly half) for that extra bus speed?