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Lemmy's equivalent to Reddit's card view
(lemmy.ml)
It's not exactly what you're looking for, but there's an open-book icon on the right-hand side of line with OP's username, the community, and the post-time that expands the content. I'm not aware of a setting to auto-expand this option for all posts, but if you're willing to click that icon you don't need to leave the feed to see the post content.
It seems likely that an extension or maybe even bookmarklet could auto-expand every post, or of course you could file a github issue to have this be added as an option.