i might be totally off with my understanding of what you are looking for

there are local signal groups where people exchange ideas and sell/gift stuff (pretty sure there are groups on telegram, whatsapp and facebook too, but i don't like these platforms that much)

we also have a local newspaper and on their website you can put small ads and offer nearly everything, from cars, houses, services and smaller things

both examples use an already existing userbase (chat/newspaper)