I reported the following issue to Tumblr:
I have setup Tumblr to post to Facebook as well. However, I have
noticed that posts published from the queue do not appear in my
Facebook timeline – only posts I publish directly. can this please be
fixed?
And this is the reply I received:
Facebook has altered the way it displays information from Tumblr and
other applications. While you should see some of your posts appearing
in your newsfeed, not all posts will appear there. This is to keep
applications from cluttering your Facebook newsfeed.Unfortunately, we can't control how Facebook displays content from
Tumblr.
This does not sound right to me: Tumblr would surely have been the author of a plugin – and failing to post to Facebook items that came from the queue does not sound like something on the Facebook side, but in the plugin. Is it possible that I am doing something wrong here?
-edit-
Why would Facebook discriminate between posts published from a queue and posts published directly? More importantly, HOW could they discriminate? Is this data provided by Tumblr to Facebook? Either way, this looks like a bug to me, and I believe it more likely that it's a bug on the Tumblr side and I am disappointed that Tumblr apparently will not even investigate.
Best Answer
Even though @FelixBonkoski's ifttt seems good, I found my solution a different way: I had already set up Tumblr to publish automatically to Twitter.. And thankfully Twitter can publish to Facebook, and this seems to work well for me - for items published from the queue or directly.