As a TLS forward proxy user who automatically redirects all HTTP to HTTPS using the proxy, I am not inclined to pay attention

But I would have guessed "Yes, they do"

As it happens, some now are accepting HTTP connections

For example, Google, Bing, DDG

Others still redirect to HTTPS

For example, Yandex, Brave

Pardon the ignorance but when did this change

Is there an obvious reason

   req()
   {
   printf 'GET / HTTP/1.1\r\nHost: '$1'\r\nConnection: close\r\n\r\n' \
   |nc -vv $1 80
   }
   
   req www.google.com 
   req www.bing.com 
   req lite.duckduckgo.com
   req search.brave.com
   req yandex.com