Well, Runic Awakening has been on Smashwords for two weeks, and in marked contrast to Amazon, there have been no sales whatsoever. Not even with promotions, coupons, Facebook and Google ads, and so forth. As a result, I've decided to go back to having it on Amazon KDP.
It'll take a few days for the book to be removed from Smashwords' vendors, so Runic Awakening should be available back on Kindle Unlimited within that timeframe.