I've encountered not being able to register using an email account that isn't hosted by one of the major commercial providers. I had to spin up an @outlook account to use for this nonsense. If it's something I don't really need to do, I often just nope on out of their bullshit instead. Similarly, yesterday I encountered a site that wouldn't let me submit their contact form if I didn't turn off my adblocker. Sucks for them, I was going to place a decent order and just had a question.