Userscript for Tampermonkey (maybe for other managers too). It just copy a table to clipboard. Pasteable into spreadsheets.

table-copier.user.js

// ==UserScript==
// @name         Table copier
// @version      0.1
// @description  Copy a table to clipboard. Pasteable into spreadsheets.
// @author       Jakub Marcinkowski <kuba.marcinkowski on g mail>
// @match        http*://*/*
// @grant        GM_registerMenuCommand
// @grant        GM_setClipboard
// ==/UserScript==

(function() {
  'use strict';

  function copyTable() {
    const tables = document.querySelectorAll('table');
    let table = null;
    switch (tables.length) {
      case 0:
        alert(`There are no HTML tables.`);
        break;
      case 1:
        table = tables[0];
      default:
        if (table === null) {
          const choice = parseInt(prompt(`There are ${tables.length} tables, which one to copy?`));
          if (choice >= 1 && choice <= tables.length) {
            table = tables[choice - 1];
          } else {
            alert(`Number is out of range, please try again.`);
            copyTable();
            return;
          }
        }
        GM_setClipboard(table.outerHTML, 'html');
        alert(`Table is propably copied. Now paste it into spreadsheet.`);
    }
  }
  GM_registerMenuCommand('Copy table for spreadsheet', copyTable);
})();

New version:
https://gist.github.com/JakubMarcinkowski/dbc55176baa98f1c636817c08ef1c493