So on the HBO website it listed Alien Covenant under "New Movies to Watch Tonight". When you go to HBO it does list it but wants to charge me $19.95 to buy it, even though I'm pretty sure it was playing on HBO a couple of nights ago. So now is HBO in the business of selling movies instead of just running first run movies if you have a subscription?
I just checked and the Free SD version has been re-added to On Demand. It's available until 3/17. At least in my region. Hopefully that means it's available for everyone.
King Arthur: Legend of the Sword still has not been re-added as a free option.