I haven’t been marketing my books very actively lately, so it’s always fun to get a notice I’ve sold copies (!), which tells me my past efforts must still be paying off. I can’t trace where readers are learning about my books, but here are a couple of places I’ve promoted my books in the past, so maybe they’re working (I know the first has).

Sandra’s Book Club started out as a way to read and review books, then for each book you reviewed you got a couple of months on the list where others could find your book to read and review. Now she’s split the review side from the author side: reviewers get free ebooks to read and review; authors pay to have their books included. Not as expensive as some services (less than $20/mo), though, so take a look:
https://sandrasbookclub.blogspot.com/2020/08/submit-your-book.html

Book Reader Magazine has two options.
1) Submit your book; $20 to be on their feature page:
http://bookreadermagazine.com/submit-your-book/
2) FREE interview (just fill out the form):
https://bookreadermagazine.com/featured-author-interview-series/

Awesome Gang is a related site and has the same options:
1) Submit your book; $10 to be featured on their homepage and in e-mail and social blast: https://awesomegang.com/submit-your-book/
2) FREE interview (just fill out the form): https://awesomegang.com/author-interview/

Awesome Gang has also “joined forces with Bookgoodie and the Author Marketing Club to create a network of sites where you can advertise your book for a package price.” This is pricier at $129, but reaches a bunch of promotional sites without you having to go to each one (I counted at least 10 sites). I did one of the cheaper, individual sites and now frequently get e-mail notices of discounts. Here’s their sales pitch: https://authoradnetwork.com/
and here’s the form you need to fill out: https://authoradnetwork.com/purchase/

Good luck and let me know if any of these work for you!