No, you cannot SLI, since the CUDA CORES are not same.
The full implementation of Nvidia’s TU104 GPU, the RTX 2080 Super boasts 3,072 CUDA Cores with a boost clock of 1,815MHz, 48 RT Cores (for ray tracing), 192 texture units and 8GB of GDDR6 clocked in at 15.5Gbps.
On the other hand, the older RTX 2080 has 2,944 CUDA Cores and 46 RT cores,, a boost clock of 1,710MHz, 184 texture units, and 8 GB of GDDR6 at 14Gbps.