Absolutely, it’s a trade within a trade really.From my "diy" experience, tin work is very hard to do well without practice.
As it should be. Down here in the states anyone with a few dollar bills in their pocket can go buy some flex, call themselves an installer and scab in a house.Flex duct is not used for general hvac in residential up here in canada - sheet metal ductwork is still used in all the new houses.