Go to https://feedly.com/i/label/feedly.history and log in. open console and write in:
document.querySelectorAll('.EntryMarkAsReadButton.rounded.EntryToolbar__button.button-icon-only').forEach(div => {div.click()})
this works for have loaded and read news, so you shoul reload website and run this command in console again until all news will be marked as unread.
