There is no official changelog from Philips Hue yet, but I can draw your attention to a software update for the Hue Bridge. Yesterday evening they seem to have started rolling out firmware version 1.56.1956178040.
With this update, the date and time of the last activity are displayed again in the settings under Accessories. For example, the last motion detection of a motion sensor or the last button press of a switch. With firmware version 1.56.1956046040, this information was missing until now.
Unfortunately, there is no quick and easy way to install the update directly. I would simply recommend a little patience here; in the end, it doesn’t matter if it takes a day or two.
In any case, there will be extensive changes in the Hue app later this year, which will ensure that this data is displayed even more prominently. But that’s another story…