Libraries
One of the biggest frontend libraries is React. This way I get relevant experience when experimenting with my hobby projects. React itself is a library and not a framework, but the makers of React urge people to use a framework. Vite can be used to create a React application from scratch easily.
HTMX is an alternative that takes a completely different approach to web development.
Sources
Frameworks
Project Ideas
A tool to visualise Google Search Console statistics. The advantage of this particular project is that it doesn’t strictly need a backend. Everything can be handled by the frontend. (Your app doesn’t necessarily need a backend)