HP Instant Ink Free plan on any printer (YMMV)

The HP Instant Ink Free plan (15-page/month) usually requires a specific printer on this list . I just tried to cancel my 30-page/month Instant Ink plan on my HP OfficeJet Pro 8740 and it gave me the option to switch to the free plan. I don’t know what other printer models/scenarios this may work on so YMMV.
Here’s exactly what I did:

• Goto the My Account page in Instant Ink
• Select "Cancel my HP Instant Ink Subscription" at the bottom of the page
• Select Other and enter any reason