I don't think you can stop the websites, but I could swear that it was recently discussed that you can put screen readers, and I think it was NVDA in particular, into "stealth mode" at startup so that whatever flag it is that the screen reader sets/waves to tell software looking for it that it's present is not set. But I'll be darned if I can remember the magic search term to find that discussion.
Brian - Windows 10 Pro, 64-Bit, Version 2004, Build 19041
It’s hard waking up and realizing it’s not always black and white.
~ Kelley Boorn