For getting a job? Express is probably less common in enterprise, but since the whole stack is JS/TS you'll have no problem porting your knowledge from that to any of the newer server-side frameworks. React is to my knowledge still the most widely used framework in modern front-end development.

Regarding self-hosting, make sure you look into isolating the RPi you use to serve your app from the rest of your home network as much as possible, and change the default password.