We already know the answer to a lot of this. Algorithms that increase "engagement" by promoting controversy promote conspiracy theories, because conspiracy theories are controversial and get everybody arguing.

The first generation of response to this was to tweak the algorithm to favor "trusted" sources, but still promote controversy. This seems to be going extremely poorly, because it's encouraging the "trusted" sources to become radicalized in an effort to get promoted by the algorithms.

The actual solution probably involves not optimizing for engagement anymore, but that's a business model change.