First validating your idea can be as simple as combining JotForm, Venmo/CashApp, Google Slides, and SMS._ Example: Zest had a Google Form allowing them to create a meal plan for users, and once they paid, they would share the meal plan in Google Slides and send the grocery list via text._
Sylvain's take: Here are more details about the flow:
Potential users would fill out a questionnaire on Jotform
On the last question, they would give their Venmo/Cashapp info
After payment, Zest (going by Salus at the time) would distribute these Google slides (the meal plan)

A few slides from Zest’s MVP
If you try their app, you’ll notice some of the tone and concepts (e.g., quick how-to videos) were already in the slides!
One caveat to the friends & family method is that they might not represent a broader audience or take pity on you instead of giving you candid feedback.
For this reason, Jason mentioned that buying traffic on Facebook and sending it to a landing page might give you a better signal. But from there, it’s ok to keep it simple if it helps validate (or not) faster.