I can create up to 2^8 key domains during Nitrokey HSM initialization.
What is the overhead of having an empty domain? How much extra space does an DKEK/XKEK domain take?
The number of key domains cannot be apparently changed later, so I’d like to know in advance.
You are only allocating slots for the key domain during initialization. That requires two bytes each. So it is save to allocate a few in case you need them later.
If you later create a key domain in the slot, about 260 bytes of memory are required.