/ip firewall filter
add action=drop chain=forward comment="Blocking Youtube on RouterOS using TLS Host" dst-address-list=Youtube src-address=192.168.50.0/24

/ip firewall mangle
add action=add-dst-to-address-list address-list=Youtube address-list-timeout=4w2d chain=prerouting comment="Detecting IP Addresses Youtube" protocol=tcp tls-host=*.youtube.com
add action=add-dst-to-address-list address-list=Youtube address-list-timeout=4w2d chain=prerouting protocol=tcp tls-host=*youtube*