How to quickly validate business in local area?

I've spent about six months working on an app and on-demand self storage service for people to be able to store things they need but don't use that often (https://www.stowed.com.au). I'm now ready to launch, but I'm struggling to think of good ways to try to find my first customers, as the paid part of the service naturally needs to be confined to my local area to start with (I'll be delivering and picking up boxes of people's stuff). So that kind of rules out promoting heavily here and places like Product Hunt.

Aside from social ads, which can be quite targeted, and old fashioned letterbox drops, I'm looking for some interesting ideas how to find customers.

The app is available anywhere, and can be used to manage stuff in your own containers (with image recognition to make it really easy to keep track of what's stored where). But the offsite storage is only in Melbourne within a few kilometres of the city.

Initial target markets are families living in apartments, people downsizing, potentially people needing to make room for home offices, as well as a few others like students and Airbnb hosts (if people ever travel again).

Has anyone faced this challenge before and have a good idea of where to start?