How can spouses ensure that a camera is being monitored, and is it permissible for them to speak through it without ensuring it is being monitored, especially with the spread of news about their monitoring?

Communication channels are not safe from being accessed by others, and there is no way to know if a camera is being monitored or not. If it is merely a suspicion, then there is no prohibition. However, if it reaches the level of strong presumption (ghalabat al-dhann), then it is forbidden, because strong presumption is considered in Islamic rulings and is equivalent to certainty, as indicated by the Almighty's saying: (Then if you ascertain that they are believers) and the Hadith: "So I assume that he is truthful." Spouses should exercise caution and modesty when using these means.