The attempts started almost immediately, but they certainly accelerated over the course of the first few days. Initially, I think it was less than 1 knock per minute, but now it’s over 8. As a comparison, I set up https://amsterdam.knock-knock.net yesterday, and it is now at 2.9 knocks per minute.

The bots though scan through all the IPs on the internet, but perhaps they bias certain IPs (local / faster response? On the bots provider network?). Will be interesting to watch this over time.