Hi,
we are not experts in the field of residence/work permit. Usually we refer to SIRI.
I agree with you that as an accompanying family member you should be able to take any job with 1 day notice, and therefore can be available for the labor market, which is one of the conditions for being eligible for Unemployment benefits from a danish A-kasse.
How the A-kasse will look at that you are depending on your spouses visa, I can’t tell. You must find out by contacting an A-kasse.
However also other requirements apply. You need to be member 1 year and meet the income-requirement. See more here: https://www.a-kasser.dk/benefits/
Your spouse can not take any job with one day notice. And therefore she will not be able to get unemployment benefits from a danish A-kasse. Therefore it will not make sense for her to join A-kasse. Only if she get a permanent residence permit, it will make sense.
Best regards,
Anders Weber, A-kasser.dk