The best solution is to change the data type of that column to varchar(MAX). Yes, I hear that you say that you can't change it, but tell your stakeholders that they have had eighteen long years to replace this deprecated and mouldy data type. It should have been done a decade ago.
If they insist on keeping the data type, they will have to keep paying for lame workarounds.
One possible workaround is to create a view on top of the table where you cast the data type. Your ADF pipeline would work against that view. Then you need to have INSTEAD OF triggers on that view to propagate the operations to the underlying table.
As I said, I don't know ADF myself, but I would be very surprised if ADF does not permit you to use a custom statement for the operation. And in this operation you would cast the data type.
But as I said, the best is to fix the data type....