After my initial small-scale launch, I made an announcement on a couple of private Slack groups to solicit interest in participating in the FunLittleAds beta. I have a beta program manual available at https://funlittleads.com/betaprogram to help potential users set up as either an advertiser or a publisher.
Currently, I have more advertisers than I have publishers. The only app that is hosting FunLittleAds is my own, a macOS app called HardG. So I'm looking for ways to get the word out and start providing the network that's going to be a place for people to buy ad spots.