You can reduce anything happening on the computer to arithmetic operations. If you can do additions and multiplications, then it's turing complete. All others can be constructed from them.
The point of FHE is it can operate on gibberish-looking ciphertext, and when this ciphertext decrypted afterwards, the result is correct.
Indeed, there are those working on faster FHE sorting: https://eprint.iacr.org/2021/551.pdf
E.g. FHE_SORT(A,B) -> (X,Y)
where Dec(X)<Dec(Y)
But without decoding, there's no way of knowing whether X (or Y) comes from A or B.
Source: II. D of https://eprint.iacr.org/2015/995.pdf
To do anything practical the server usually needs to provide the client with gigabytes of per-client-key encrypted seed data.