dither when "swapping L+R channels"

I’m simply swapping L+R channels of a 44.1/16bit recording, so the left becomes right and right becomes left…
I’m 99% sure I do NOT need dither on for this?, am I correct?

That is correct. You are not changing the actual audio sample data, you are just “moving bytes around”.

I forget which channel comes first, but with WAV files the left & right channels alternate, so with 16-bits audio, you have two bytes (16-bits) for channel-1, two bytes for channel-2, two bytes for channel-1… etc.