Agreed with the article, but to add to:

> The ability to update the firmware may also be locked down. You should have full control over firmware updates.

Bizarrely, for DOCSIS modems, even if you buy your own modem, the ISP has control over firmware! They can (and do) push any arbitrary firmware to your modem. The manufacturers go along with this for some reason.

So make sure to separate your modem and router too.