In Firefox, on Linux, behind a VPN and firewall with ad blocker, I run 5 different privacy/ad blocking extensions. I keep hearing about adds, but not seeing them.
Supposedly Youtube now is getting more agressive on this? I wouldn't know. Haven't seen a Youtube notice about it yet.
But really, I dream of the day youtube is replaced by something else. Fracture Youtube into 1,000 pieces and scatter it into the wind.