Is the transaction included in the fundamental ignorance [Jahalat al-Ja'l], and is it permissible to work on a platform that initially offers tasks with an unknown wage, where the wage is disclosed after the task is completed based on the work's accuracy? And is there any objection to evaluating the worker if the mechanism for calculating the accuracy percentage is concealed from him?

Ignorance in a ju'alah (reward-based contract) only ceases to exist when both parties to the contract know the amount of the ju'al (reward). If the worker does not know the ju'al, it is unknown to him, and thus ignorance is present. Engaging in فاسد (invalid/corrupt) contracts is considered haram (forbidden) by many scholars, and some have even stated that proceeding with an invalid contract is haram. However, if the ju'al is known but varies according to the worker's evaluation based on regulated rules that do not lead to dispute or gharar (excessive uncertainty), then this is not considered ignorance that affects the validity of the ju'al. This is similar to the jurists' saying: "If you sew this garment in Persian style, then for one dirham; and if you sew it in Roman style, then for two dirhams," which is valid according to the Hanafis and one narration from Ahmad.