It’s just a version of the garmin firmware on your device. It’s bound to the CIQ version on your device.
To check yourself if your device supports CIQ System 5 already, simply check the CIQ version on your device. Here’s a short overview of which CIQ version supports CIQ System 5:
Be aware, new flagship devices like the Fenix 7 and Epix 2 are not supported yet!
At the date of writing this, only following devices do support the new CIQ 5 System already:
This list is copied from following announcement (at the very bottom):
Connect IQ System 5 Announcement by Garmin
New devices will very probably get a firmware update from garmin soon as you can see in the link above. As soon as your device has the correct firmware that supports CIQ System 5 my watchface will automatically support the new features on your device as well.
When this will happen does just depend on garmin…
As far as I’ve heard, Fenix 7 and Epix 2 do already have beta firmware that supports CIQ System 5 so those devices should get official support (at least for european devices) in the near future.