Not all military planes are going to actually have ADSB, obviously. Also even the unfiltered stream requires an ADSB receiver somewhere.
Yes, that's true, but I'm still struggling to understand the market fit for "where are the military aircraft". You would presume the people who need to know this information (ie those people for whom this is actionable data) already know this to a sufficient degree?
They do. Until people who have this information decide to stop sharing it with you.
In my experience, military aircrafts are visible in flightradar most of the time. However, if they are flying in a group (e.g. choppers), usually only one of them is visible.
It's not true that commercial services filter out military aircraft with ADS-B. In fact, FlightRadar24 even lets you filter to only show military aircraft. I see over a dozen flying near San Diego right now.