"I will use eggs in today's meal."
That bugged me as well. I know you can you ごはん but that wasnt a choice.
That makes perfect sense - thank you! I wish there was a way to save threads like this that serve as great teaching aids
Duolingo has got to get better at explaining grammer. Nowhere else at this level have i come across ni and wa being used together as a particle
Is there any credibility in the には? Like what does it imply grammatically?
には is essentially が reverse in places emphasis on what precedes it. as @bmpurifoy explained before は by itself is generic but には (also では) place emphasis. に is still acceptable because in this case, it indicates direction. "IN today's meal" は is generic and does not indicate direction therefore is wrong.
Hope this helps :)