Seems like it should work for arbitrary byte strings (any charset, any encoding)but obviously the performance characteristics will differ because of non-uniform distribution. But that happens even in ASCII.
Lexicographic encoding of UTF-8 byte sequences matches lexicographic order of the sequence of Unicode code-points. So you can sort UTF-8 strings as byte strings. Not that sorting by code-points has much meaning, but you can use the Unicode collation algorithm first.
TIL, thanks. That makes sense given how the length prefixes look like but I never thought about it. I wonder if this was by chance or if the UTF-8 creator thought about it.