(trying to consolidate the many topics I have opened on this, let me reply here):
From Netlify form 404 with netlify dev (gatsby site) - #7 by hrishikesh
That’s unfortunately not true: I have seen the form being submitted in the console, but it actually not being collecting form data when pushed to the live site. I have had to create a separate staging site and test it by constantly pushing to it until I got it right. Simply in dev there is no way to properly test form submission, unless there is something I’m not seeing or looking at that I should.