"What day of the week is October tenth?"
Something with using the computer instead of my phone leads to more issues like putting in the right answer and being told its wrong while the answer i put was exactly the right answer. As well as 'type in English' questions being a little inconsistent but exact on what they want.
Careful... the particle は is a contextual particle, and as such is used for marking topics.
Topics are always something that is known. An interrogative like 何曜日 is by its very nature unknown - we are asking about it - therefore it can never be a topic of the sentence. In this sentence, 何曜日 is a subject and therefore is marked by が, but it is NOT a topic and cannot become one.
That is why interrogatives like 何~ words and どこ / どれ etc. always take が and never は.