Gatsby Hydration Issue

I recently made the error of using Gatsby instead of Next JS for the development of a Landing Page. Styled Components were used and everything was working fine in dev mode. In production mode, the hydration of the page was not working. Therefore, the CSS of the page was not shown correctly, and it took me some time to figure out what was going on. So to spare you some time to resolve the issue, here are three links to solutions and explanations: