Is it permissible to cast the left hand to learn to eat with the right, after becoming accustomed to eating and doing all work with the left hand, and people say that this is forbidden?

Islam has regulated everything, including how to eat and drink. The Prophet, peace and blessings be upon him, guided Omar ibn Abi Salama, may Allah be pleased with him, to say Bismillah (in the name of Allah), eat with his right hand, and from what is directly in front of him. The Prophet, peace and blessings be upon him, also forbade a man from eating with his left hand, and when the man excused himself by saying he couldn't, the Prophet supplicated against him. It is sunnah to use the right hand for all matters of honor, such as ablution and eating, and to use the left hand for matters of removing harm. Therefore, one must accustomed oneself to applying the Sunnah and beware of contradicting it, as Allah Almighty says: ﴿And let those who oppose His command beware, lest trial befall them or there befall them a painful punishment.﴾ [An-Nur:63]. Furthermore, putting the hand in a cast is not an appropriate solution.