Echo chambers are not dependent on having an algorithmic feed. It just matters that the people you talk with and the information you consume, etc, filter out dissenting opinions from what you hold.

Lemmy is still very much an echo chamber simply by virtue of the people who tend to be here. But we can balance that with time spent on other platforms, IRL relationships, etc.

An echo chamber is an echo chamber. Whether natural or artificial. Lemmy is extremely one sided. Dissenting opinions are not tolerated nor welcome (from a political standpoint). Perhaps less so than reddit as Lemmy user base is much smaller.

In Bluesky you choose your own algorithms by adding feeds you follow.