Here’s what Emirates says:- If you booked your ticket on or after 1 April 2021
You can change it for another destination in the same region and in the same travel class for no extra charge. If the itinerary on your original ticket did not include Dubai, then you are only able to change your flight for a similar itinerary that does not include Dubai.
Doesn’t seem like the origin can be changed? Also, it’s quite unclear whether they charge a fare difference?