This is a fork that orders tabs every 5 seconds. If tabs are already ordered, nothing is changed.
https://addons.mozilla.org/ru/firefox/addon/order-tabs-by-domain-period/
If you want to install this extension, use releases. Approval from mozilla will take some time. It's the same extension as in this repository, just signed.
This is an extremely simple browser extension. You push a button on the toolbar and it orders all the tabs in the current window by domain. One day I may put some actual design effort into it, but for now this is all you get.