@arc99 you still don't understand end 2 end encryption. Yes man in the middle decryption can be done. First for this to happen you need to accept the certificates of the firewall ( which in terms of a home PC you can't force anyone to do ). Second even if you can decrypt the https packets , you can still put an additional layer on top which only you and the reciever has the keys too.
To give you an example you can easy write down a base64 encoded binary blob in any text field on a website. If this binary blob has been encrypted before noone will be able to tell what is inside.
So breaking https is useless if someone really wants to hide informations. So no your deep packet inspection is totally useless. The only thing you know is that someone did put strange stuff in a text on a website.
@arc99 the same way as you did encrypt it ??? with ggp ?
https://stackoverflow.com/questions/35584461/gpg-encryption-and-decryption-of-a-folder-using-command-line
???? the needed certificate are exchanged by for example a matrix / telegram or personal ????
And don't underestimate kids ... Or better asked yourself how did they get porn in the 80s and 90s ??? ( and yes they did )
PS: and honestly imho this hole "protection talk" is totally nonesense or are parent's not anymore capable of protecting their kids? Tell my one reason why a kid < 16 should have access to internet without supervision ? An Emergency Call can still be done without internet.
This hole discussion is like if you would had let a Porn VHS in the 80's unlocked in the living room and your kid unsupervised for hours in the living room. Would have someone called in the 80's to audit if your porn has been stored kids savely you would have gone crazy.
PPS: Just because you don't have statistic's how many kids watched adult content in the 80's or 90's doesn't mean it didn't happen !!!