Can RadixSort be Ω(n log n)?
The more accurate time complexity analysis for  Radixsort gives time complexity as $O(kn)$-time where $k$ is number of digits, or keys (radix is defined as the base by which digits or keys are formed, hence the name radix sort). 

So, radixsort can be $\Omega(n\log n)$ if you have $\Omega(\log n)$ digits in the numbers you are sorting. For example, if you are given numbers 1 to $n$ in an unsorted list, then radix-sort will do the sorting in $O(n\log n)$ time.

See https://en.wikipedia.org/wiki/Radix_sort.