People use "Serverless" to mean different things, but the trendy usage is something like AWS Lambda. It's not actually "Serverless" because the server does exist on AWS server. So what they actually mean by "serverless" is "not having to manage server". I think what you're talking about is SPA (Single Page App). These are the trendy Javascript frameworks like React and Vue, which construct UI on the frontend instead of rendering server side. This has SEO issues like you said. So they came up with server side rendering of the client side rendered apps, so that the UI is already rendered when the page loads for the first time. But nowadays you don't have to worry too much about these things if you follow the best practices because search engines like Google have started handling SPAs well.
People use "Serverless" to mean different things, but the trendy usage is something like AWS Lambda. It's not actually "Serverless" because the server does exist on AWS server. So what they actually mean by "serverless" is "not having to manage server". I think what you're talking about is SPA (Single Page App). These are the trendy Javascript frameworks like React and Vue, which construct UI on the frontend instead of rendering server side. This has SEO issues like you said. So they came up with server side rendering of the client side rendered apps, so that the UI is already rendered when the page loads for the first time. But nowadays you don't have to worry too much about these things if you follow the best practices because search engines like Google have started handling SPAs well.