Or even worse, due to defederation, they may not all point to the exact same content.
Without further investment either from lemmy or the search engine's side, they are probably seen as distinct sources, not aggregated. Which makes each individually less relevant and less likely to show up .
Also note none of the adresses above contain 'lemmy'. How would users search for content on lemmy in these cases? Can't do "technology site:lemmy", or?
But I can say, lemmy content is visible. Haven't seen it on the first page of ecosia yet, but on page 2 or 3.
This is relatively simple to solve from a technology perspective. You just incorporate the canonical URL meta tag on federated sites that reference the source URL. It'd be trivial to implement, provided the authoritative URL is known.