How do you find your first 100 quality beta testers? (Building a RaaS)

Hey PH community,

I'm at that classic "ready for users but have no users" stage of my journey and would love some advice from those who have been here before.

I've spent the last few months building what I'm calling a RaaS (Rizz as a Service). It's an AI keyboard for Android designed to help people win conversations with genuinely witty, frame-controlling replies, not the cringey, robotic stuff that's already flooded the market.

Now that the MVP is ready, my big question is: What are the best strategies you've used to find your first 100 quality beta testers?

I'm not just looking for numbers; I'm looking for people who will actually use the product, break things, and provide brutally honest feedback. I've seen everything from Reddit posts to small ad campaigns. For those of you who have launched a B2C app, what actually worked to get those crucial first users who genuinely cared?

Is building a Discord community from day one a must, or is a simple email list enough to manage feedback effectively at this early stage?

For context, the project is called RizzKit Pro: AI Wingman. Right now, my entire "system" is just driving people to a landing page where I can collect their Gmail to add them to a closed Google Play beta. (If anyone wants to see the product I'm talking about and the landing page I'm using, the site is https://www.rizzkitpro.com. Of course, I'm happy to add you to the beta list if you sign up or DM me).

Any wisdom, horror stories, or "I wish I'd done this instead" advice on finding those initial, invaluable users would be hugely appreciated.

Thanks for the help