Any recommendations on pre-launch promotion (beta ver.signup) platform other than PH?

Hey everyone, happy Wednesday! I was wondering if you guys could recommend some platforms to promote pre-launch (beta ver) platforms for wishlist sign-ups! My tool (shadow.do) will give few months free for beta sign-up users when we launch on PH but not sure which platforms are appropriate. If you have any ideas, could you pls kindly recommend? Thanks :)