Product designer for 10 years. Chief Product Officer for 4. Validated many MVPs and product concepts pre and post funding raise, with current customers and without.
In almost all cases, you can validate the product idea through non-technical means. The notion that you must raise before you can build anything is a classic "never done this before" misconception. And it will signal to an investor that you don't know what you're doing. Sorry if that sounds harsh – but its a true read on the situation and the times we live in.
Investors simply expect you to have an MVP, users / customers, and traction metrics before they give you a cent. The investment will be to amplify something that, to some degree, already works – not to fund a greenfield, exploratory build.
Back to non-technical: Its possible to scrap together an MVP for most products using existing products. Especially the marketing and acquisition funnel stuff (more important than most people think).
The actual app is more difficult, but can be done. Either through shaving off features to a very small subset. Or by "wizard of oz" approach. Where the front end of the software exists (made from a wordpress template, webflow, etc) and the backend is manually curated by the founder – meaning a human plays the role of the software.
Really slow. Kind of lame UX. But you can acquire customers and test your idea this way. I know because I'm personally using / paying for a service like this right now.
Happy to look at your exact case and develop a plan.