I've been searching for a "full-stack" Web development job for the past 8 months this year, and aside from industry incompatibilities, the biggest headwind I'm facing finding an employer that recognizes front-end development is so much bigger than how you arrange your JavaScript to enable interactivity.
I have experience with React; my last career position allowed me to go from 0-100% confidence/competence with Svelte in 4 months. But employers want to see some equivalent of "3-5 years experience with React" and structure their shitty technical assessments similarly, and I've really had a problem trying to find the right way to show I'm just as qualified.
Runtimes: a lot of frontend JS engineers don't know what these are. Being able to explain them (and the difference between Node and Deno for ex) is a good answer. For backend jobs this is a hard requirement, but when I see "Node" in a frontend job listing I assume it means "can install packages from Node."
Frameworks: (like Next) it depends. If I'm hiring for an app already built in one, maybe. A general answer like "SSR is a problem with React" and "this framework solves that problem this way" is useful.