I have recently put together a list places to buy an app, mostly sourced from [1]
https://microacquire.com/
https://flippa.com
https://www.motioninvest.com/
https://investors.club
https://indiemaker.co
https://feinternational.com/sell-your-website/
https://empireflippers.com/
https://exchangemarketplace.com/
https://helloexit.com/
https://www.microacquisitions.com/
https://www.bizbuysell.com/
https://www.sideprojectors.com/
https://onfolio.co/
https://zeroacquire.com
https://arraycapital.com
Microns.io
Duuce.com
https://www.facebook.com/groups/flippingwebsites/
northboundgroup.com
websiteclosers.com
https://nanoacquire.vercel.app/
https://www.bitsfordigits.com/
https://acquirebase.com/
As a buyer, most of these are not so good, and I am only using microacquire. (reasons: too few listings / all listings are just Amazon affiliates / buggy / no one replying).
Not sure on the seller side, but I think microaquire + indiemaker + sideprojectors would be a good combination of places to list.
[1] https://www.indiehackers.com/group/business-for-sale
Also unsolicited advice: you app looks cool, but I only saw it in the wiki! Put a big wide hero style screenshot on the home page.