(The extension displays some optional ADs. If you don't wish to support me, you're welcome to disable it in the settings.)
If you copy some text to Office, Outlook or ThunderBird (or in fact any rich text compatible application), all the formatting (italic, bold, font size, etc) also gets copied. Usually to copy the text-only version, I copy from browser, paste it into notepad, then copy it again.
Copy Pure Text gives you an option to copy text without the formatting. It will add a ‘Copy as Text’ menu item in the context menu.
Check the addon options for more customization possibilities.
Note to Users:
If you find this add-on helpful, kindly consider to submit a review.