There are realistic situations where galactic O(n) sorting algorithms exist, right? 32-bit integers can be sorted in O(n) using 2^32 words of memory, using bucket sort[1].
If objects have a maximum size of 4 GB (= 2^35 bits), then arbitrary objects can be sorted in O(n) using 2^2^35 bits of memory.
If objects have a maximum size of 4 GB (= 2^35 bits), then arbitrary objects can be sorted in O(n) using 2^2^35 bits of memory.
[1] https://en.wikipedia.org/wiki/Bucket_sort