Glad to see you back on usual form
Perhaps you forgot about google, which tells you in about 10 seconds that DiTBho is all over the internet asking for help
That wiki is now a 404 error, so nothing to update. Digging around, it seems the original dev transferred/sold the business to another company which, like all Magento devs, is making money from M1 to M2 data transfers. That company then took the M1 matrixrates offline.
This is the Magento business model. The software is free and open source. The entire ecosystem around it makes money from integration, upgrades, and admin.
The guy who set up M1 for me did look at M2 (it was out then) but it was full of bugs and barely usable. But it would not save money, because nobody talks to you unless they can make money out of you.
That's why I asked here if anyone uses it. This forum is about people helping each other. I've made a big number of posts here helping people too, and unlike you without being rude.
Archive.org may have a copy but it is currently offline.
UPDATE: it turns out that the two CSV import/export buttons were disabled, via a setting in an XML file app/code/community/Webshopapps/Matrixrate/etc/system.xml. Why, no idea! There are indications that some Magento or Matrixrates patch disabled them, because Magento has had loads of historical back doors via XSS etc and any file upload facility is a bad idea if you have that; the fact that those buttons are visible only to admins doesn't help if the attacker gets admin access.