I was reading on how ISPs in many countries block access to many sites. This got me wondering -- How do ISPs block sites in the first place? I found answers here, and reading through, it became evident that ISPs usually drop connections going to these blocked domains on their DNS servers, which can be easily circumvented by using a different DNS (optionally also using DoH to a non-compromised server).
I then read on to find that ISPs also block domains by their known IPs, so using another DNS wouldn't fix this issue. This led me to think -- what if the server was on a dynamic IP?
The devil's advocate of my mind quickly told me that all the ISP had to do was to run a dns lookup on the domain itself to find the current IP and block that. But then again, what do you guys say?