How to check if a site uses HTML1 or 1.1
I am always trying to keep the post short, just the information that is required, nothing more. This one will be the shortest ever :D
Open you terminal and type this command, change the domain.name to an actual domain name:
curl -vso /dev/null --http2 domain.name
The output will look something like this:

Fourth line: GET / HTTP/1.1
Enjoy!