I wouldn't classify every monolingual person as trapped in an echo chamber

Simply being something isn't an echo chamber, you have to have a thought or opinion being shared by the group. If every person you interact with only speaks one language, and they all share that one language is the best method of communication, that's an echo chamber.

Use social media how you like

I agree. Although it is useful to be aware of your own biases.

the solution to echo chambers is going outside and touching grass not forcing yourself to interact with every community on the internet.

Assuming you don't mean literally "touch grass", the solution is seeking out opinions/thoughts outside of your echo chamber. That doesn't necessarily mean forcing yourself to interact with terrible communities, but being aware and understanding (but not agreeing with) them.

Although I again refer to using social media how you like is fine. No one needs to be exposed to certain communities. It's not wrong or lazy or bad to ignore certain communities or viewpoints, especially toxic ones. However you should be aware that they exist and it can be helpful, if you choose, to understand where they come from.

As a harmless example, if you don't like brussel sprouts and none of your friends like brussel sprouts, it may benefit you to try brussel sprouts or to seek out and talk to or read about people who like brussel sprouts. You can still at the end of the day dislike brussel sprouts. You don't have to change your opinion. But now your opinion is more well rounded.