Qvatra

const data = Object.entries(сюда кидаете свои данные);

const years = Array
  .from(new Set(data.flatMap(n => Object.keys(n[1].G))))
  .sort((a, b) => a - b);

const columns = Array
  .from(new Set(data.flatMap(n => Object.values(n[1].G).flatMap(Object.keys))))
  .sort();

<TableHead>
  <TableRow>
    <TableCell rowSpan={2}>regions</TableCell>
    {years.map(n => <TableCell colSpan={columns.length}>{n}</TableCell>)}
  </TableRow>
  <TableRow>
    {years.flatMap(n => columns.map(m => <TableCell>{m}</TableCell>))}
  </TableRow>
</TableHead>
<TableBody>
  {data.map(([ region, { G } ]) => (
    <TableRow>
      <TableCell>{region}</TableCell>
      {years.flatMap(n => columns.map(m => <TableCell>{G[n]?.[m]?.value ?? 0}</TableCell>))}
    </TableRow>
  ))}
</TableBody>