Thanks, but no. I’ve realised now that I accidentally deselected English as a language option and saved changes (I saved changes because I was testing the “Auto expand media” option). But I was a bit mislead by the little note above the languages which says “Warning: If you deselect Undetermined, you will not see most content.”. It made me think that I needed to make sure that “Undetermined” is selected in order to keep seeing most content, because that’s what it sounds like in its wording. So I re-selected “Undetermined” and saved changes, and it caused my posts to disappear; I just didn’t notice immediately because I was busy transferring my subscriptions from this account over to my new one. I’m still not sure what that note was trying to say, but I’ve fixed it now by selecting English.
What makes it a bit more confusing is that when I select English, “Undetermined” becomes deselected, which is what the note is telling you not to do; this must be what compelled me to select “undetermined”, because selecting anything else deselected “Undetermined”. It’s only after you save and completely refresh the page, that “Undetermined” suddenly becomes re-selected again, but English also remains selected at the same time.