has "altimeter" listed as one of the sensors built into the Fitbit Charge 5 (so no "flights of stairs" tracking.) The Charge 5 does not have an altimeter (per Fitbit rep in Fitbit community board.)
It is also missing the Agenda app available on the Charge 4. The Charge 5 doesn’t have any music controls either.
I see the Charge 5 as more of a "Luxe XL" with EDA, ECG and Fitbit pay.