If you're determined to keep your Google account airtight with a security key, you might have an easier time getting started. Google has made it possible for G Suite and Cloud Identity users to register security keys using both Chrome on Android devices (using at least Android 7.0 Nougat and Chrome 70) and Safari on Macs (13.0.4 and later). This includes both keys you've registered independently as well as ones from the Advanced Protection Program for enterprise users.
The option is available to everyone who qualifies. It's not a shock that Google would expand support. Both Safari and mobile Chrome are major browsers for their respective audiences -- if you can use them to add a key, you might be more likely to use one (whether it's a dedicated device or your phone) in the first place. That, in turn, should prevent some account hijacks and other intrusions.