In the mid-2010s, we barely had any apps in our native language and popular coupon and review sites were lackluster in our neck of the woods.
So me and some old uni colleagues got together to make a WhatsApp based "wtf is going on right now and right around here"
think Groupon meets yelp meets Google maps meet trending topics. The idea was that local business would post deals and events and people would comment on it giving stars on real time, with geolocation. So you could see what was going on right next to you, and business owners only needed WhatsApp installed to post new topics.

We... failed to go viral. That simple. Things get frustrating when infinite no-questions-asked venture capital is not available.

Then me and the other founders got very lucrative jobs in former British colonies and that was it.

This idea might still work nowadays, but it would be reeeealy hard to navigate around Whatsapp's terms of service.
Good luck to anyone who might want to try.