if your quasar dist structure like
dist/spa
css
fonts
icons
img
js
favicon.ico
index.html
use code
const quasarServe = require('quasar-serve');
const app = express();
app.use(quasarServe({
distPath: path.join(__dirname, './../client/dist/spa'),
replaces: {
baseUrl: config.baseUrl,
},
}));