@d-v You may benefit from this video:
https://www.youtube.com/watch?v=6UULahZUMQM&t=1063s
The following features can be used to determine readiness:
First, your overall sleep data, primarily how long you slept.
Second, your gained resources overnight.
Third, your nightly HRV score
Fourth, your current Form result (the difference of CTL and ATL from previous day)
I may be temporarily forgetting some other factors as my coffee starts its morning magic on me.
While I understand this is not one discrete number to use, for me I look at all of this data anyway, and a readiness number would unlikely tell me more than what the above does. I can see where Suunto may want to have such a feature to appeal to new users looking at Garmin, etc. from a feature standpoint, but as individuals, we are better served understanding the above factors for our training.