If your purpose is plain simply to upload a file which can handle by backend service than Gatsby is good enough assuming you have other content pages which will benefit from faster page loads for those Headless CMS driven pages. But if you have more logical/functional aspects like deciding content/personalization at server side of web application than choose NextJS.

I have experience with Hugo and Next.js, but not with Gatsby. I would go with Next.js. However, I used Astro for my last project, so I would recommend Astro. Astro is much faster and you can use almost any frontend framework if you need to.