TechPowerUp does note that only the $1,499 GeForce RTX 3090 has an NVLink connector, the other Ampere-based desktop cards will not support multi-GPU rendering.
Furthermore, those wishing to use NVLink with GeForce RTX 3090 cards will also need to buy a new bridge. NVIDIA adopted a new, smaller connector and this will set you back an extra $79.99. NVLink is mainly for the compute market and NVIDIA is steering those users towards its datacenter products (previously this lineup was called Tesla).