難 compatibility form

It represents 難, meaning “difficult” or “hardship.”

難 appears on Western Zhou bronze vessels. Shuowen Jiezi, an early Chinese character dictionary, says 難 first named a bird; writers later borrowed its form for “difficult.” Older Chinese also used it for calamity and a rite to drive off spirits, later written 儺.

Why does it become 難?

Text normalization, a cleanup step, maps it to 難.

That keeps the reading but loses which encoded form was present. Unicode defines 難 + U+FE01 (an invisible variation selector) to preserve this form through normalization.