It would require a very little work:

• add type: 'dark' to theme.ts
• set panel background to pallete color
• save to local storage + add button to right bottom menu
• Optional followup: add dark MapLibre style

// src/helpers/theme.ts
const theme = createMuiTheme({
  palette: {
+   type: 'dark',
    primary: {
      main: '#556cd6',
    },

cc @Flohhhhh - i think you were asking for that