How do you actually validate a B2B idea before writing a single line of code?

I'm in the early stages of a B2B tool targeting small business owners and I'm trying to do this the right way, validate before I build anything.
I've already tried a few things that haven't really moved the needle:

Cold DMs (No replies)
LinkedIn outreach (Also no replies lol)

I know the Mom Test exists and I've read about intent-based outreach, but I'm curious what's actually worked for people here in practice.
Specifically I'm wondering:

How did you get your first real conversations with potential customers?
What signals told you the pain was real enough to build for?
What did you wish you'd done differently before writing any code?