Take most subreddits. The people in them hold a view and then it gets amplified everytime someone else adds to that point.

Theres a reason bitconnect worked so well on some people. Theres a reason a lot of people fell for the meme that bitcoin is old and useless while shiny new crypto projects are better.

If we are talking about the following definition of an echo chamber then yes they exist.

“an environment in which a person encounters only beliefs or opinions that coincide with their own, so that their existing views are reinforced and alternative ideas are not considered.”