Hard to say where it comes from. The sequences look like ansi escape sequences, but they are not complete. For further analysis, I would need the complete Tramp debug buffer (tramp-verbose shall be set to 10). But this cannot be analyzed here on sx. Perhaps, you ask on the Tramp mailing list?
Tramp does not use insert-directory-program. It has its own mechanism to detect a proper ls program.
Dired is not involved at all. It calls insert-directory, and let the local implementation, or the Tramp implementation run.