8. I have used Gatsby in the past and most of them use Netlify form submission, or some third party (https://itnext.io/a-comparison-of-static-form-providers-2adc51c87053). Without using a third party solution, I am not sure.
Great link to some static form providers, Ajeet!
Here’s another project that might fit the bill for @Verhoeckx : https://liquidforms.io/.
PHP, but still in development. No experience with it, seems promising tho.