Dear GaRoMeSi
For your safety, the Nuki relies on a panic lock. In other words, a key that can be turned on the inside and outside, or, as you have already written, a knob on the inside.
This is the better option anyway. The knob is unscrewed and fitted with an adapter, which is then inserted into the head of the Nuki. The version with the key also works, but it can happen that the key slips out a little bit when it is in a horizontal position.

From the outside, you can connect the power to the mounted Nuki with a USB C cable directly to the battery. This prevents it from being empty when it arrives in the flat. Otherwise, the battery lasts approx. 10 hours after charging. 3 to 5 months.
The Nuki 3.0 Pro has a little more power consumption with its built-in WLAN module.
But if you can operate the lock with the key outside, because there is a knob inside with the Nuki, you can open the lock analogue and then plug the power back in.
have fun with it, it's a pleasure
greetings Reto

There are locks with double cylinders where a key can be inserted inside and you can still lock and unlock with the key from the outside.
I have something like that in my rented flat.
But your idea with the knob certainly makes sense.
Whereby you dismantle the knob itself and mount the Nuki adapter instead of the knob.
I have the Nuki 3.0 Pro with the integrated battery and it lasts about 3 - 4 months.
You don't have to worry about an empty battery.
When the battery is empty, you can open the door with the key from the outside.
Respectively from the inside, you can turn the round "turner" of the Nuki by hand to open or close it.
By the way, Nuki announced a new lock at the IFA 2023.
It will be released in October/November and will offer Matter over Thread.
That means no more power-hungry WLAN, but efficient thread radio.
However, this requires that you have a thread border router (Apple TV, Apple HomePod, Amazon Echo, Google Nest Hub, Samsung SmartThings Hub, ...).