Hey everyone?look, I haven't released in two years (I'm saving up to rapid release either later this fall or January, I haven't decided) I've kept my sales stable with Freebooksy / FussyLibrarian / Bookspry, the occasional BookBub's and StoryBundles, and Kickstarter. But my main thing is BookFunnel and StoryOrigin.
I use both to:
1) grow my mailing list. Their mailing list builders work because folks who download your readers magnet (short story, novella, novel, etc.) are highly motivated by your writing. They aren't participating to win a gift card. In addition, you can follow up with them, romance them a little, and sell them on your NEXT book.
2) a lot of people will download your book, and then unsubscribe before giving you a chance. Sales promos give you a chance to put your books under their noses again. They'll click, realize, "Hey, I like this author."
Here's my Sci-fi Newsletter Builder:
https://dashboard.bookfunnel.com/bundles/board/1vdma82jxuSci-fi newsletter builders never have as many participants as Fantasy / Sci-fi Builders, but the CONVERSION to downloads and followers is higher.

Here's my Sci-fi Series Sale:
https://dashboard.bookfunnel.com/bundles/board/c2caoeplra
Hope to see you there!
CG