Dear All,
I need to Block Facebook mobile app, already blocking from 7Layer, which is working for Web platform, but somehow skiip mobile facebook App, Please help me asap.
Not possible.
User can just use DoH or VPN and bypass everything.
I do block this at work using another appliance, but it takes SSL re-termination with custom deployed certificate authorities. We have to filter the internet for CIPA compliance in K12 education spaces here in the USA. Not something that is feasible if you do not control all the endpoints connecting.
For those wondering, no root CA installed, no connectivity. As with most enterprises though.
This we do as well, but you need 100% control of all clients connected to your net to do that. That would exclude all home net.
Let me know please if something of what you have been recommended worked out. I got stuck with the same task and would be thankful if you shared the solution. Many thanks!
buy FortiGate instead 
Nothing will help if you do not have 100% control of all clients. User do not have admin rights. Then you can use some like Forcepoint, to intercepts all https. You prevent user from installing apps etc.