I think the answer is just the change the text domain by varchar(max) -that's was my answer-

Because: "If you assume that there is no duplicate data across both tables, then which of the following are workarounds?"

If you are assuming there is not duplicate rows is not necesary UNION ALL sentence.

In other hand I think the use of UNION ALL has a better performance insted of UNION sentence because avoid the check of duplicate rows. What you think?