Hello again, there's nothing that can be done from the Azure AD side. If you really need to make this application comply with protected app or app protection policies, the developer has to implement the Intune SDK.
That being said, and out of Azure AD boundaries, I will test the aforementioned application and see if there's something that can be done from the Android side and come back to you ASAP.
Let us know if you need additional assistance. If the answer was helpful, please accept it so that others can find a solution.