Indeed, there are dozens of solutions available and as such the choice for one is quite subjective. For me, Jigsaw was a natural migration given the PHP base, with Blade + Markdown templates.
Sure; it's a good SSG indeed. What I mean though is that you're using the SSG as a framework, an whenever you change the framework, you'll have to more or lesd rewrite your app. Using Gatsby you're writing your site/app/whatever using standard (JSX) using a library (React) - makes migration much easier later on. Not saying you're approach is wrong, I just think that it's time to stop writing web sites and rather start writing web apps (which may be implemented by a SSG, and can be just as static) ;)
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