See HTTPS Browser Recommendations on Wikitech.
Ever since Wikipedia, MediaWiki, etc., completely blocked Windows XP (and any other systems without encryption deemed good enough from reading or accessing the sites in any way), there is definitely no way MSIE 6 is in any way supported! IE 7 on Vista is sadly the earliest I imagine is still allowed any access at all.
Too bad for anyone on a system which can't be updated — nothing for you!
Windows Vista was released in 2007, Windows 7 was released in 2009, and extended support for Windows XP ended in 2014. People have had over a decade to migrate to a more modern operating system. At this point, the only defensible reason for being stuck on XP is because your work environment requires it (and personally, in that situation I'd be looking for a different job).
The MediaWiki software still supports IE6 for its HTML web pages. I test this about once a year for unrelated reasons with a local MediaWiki install on BrowserStack (with tunnel). It still works.
Wikipedia and sister projects by Wikimedia Foundation, are indeed no longer accessible in IE6. This is indeed related to encryption. IE6 is not capable of modern encryption. It is also true that we care about your privacy and security, and want you to be protected from third parties that may be eavesdropping your connection.
But, the fact that users of IE6 are insecure is not by itself a reason to block them. In fact, Wikipedia does not "block" any web browsers. The HTTPS technology involves encryption. The website has a list of encryption methods it supports, and your browser as well. If both support the same method, then you can browse the website.
If Wikipedia were to allow the old IE6 encryption method, then that means you (on a modern browser, not IE6) can be spied on as well, because anyone between you and Wikipedia on the Internet can "downgrade" your connection to IE6's encryption method; see what you are reading on Wikipedia, and re-encrypt in a modern way toward you.
The only way to keep everyone else safe, is to keep IE6 out. This was not an easy decision.
For more information, see HTTPS recommendations. Specifically, note that users on Windows XP can still access Wikipedia by using Firefox ESR 52, which does support good-enough encryption!
