I always unsubscribe from corporate newsletters, so I don't get a whole lot of them. And in any case, this wasn't a corporate newsletter.

I delete any mail from Airbnb, Uber, etc that isn't a receipt for a service they provide.

As do most people.

How would you want them to notify you of a substantive policy/TOS/etc change in order to ensure you see it?

Alert me on the web page the first time I log into my account after the policy goes live.

Bingo.

I just logged into my Airbnb account and there's a notification about this policy change. It links to a page with the same text as the email notification.

Notification text: "We’d like to use your information to help fight discrimination. Visit your Privacy settings to learn more or opt out."

When I logged into Airbnb to fix this opt-in non-sense, I saw no such message.