Here is a list of all namespaces with brief descriptions:

[detail level 123]

NBotan
NAES_AARCH64
NARIA_F
NASN1
NCamellia_F
NCamellia_GFNI
NCert_Extension
NCMCE_CT
Nconcepts
NCryptoBox
NBOTAN_DIAGNOSTIC_IGNORE_DEPRECATED_DECLARATIONS
NCRYSTALS
Ndetail
NCT
Ndetail
NDilithium_Algos
Nfmt_detail
NFPE
NHTTP
NKeyPair
NKuznyechik_F
NKuznyechik_T
NKyber_Algos
NOCSP
NOIDS
NOS
NPCurve
Nbrainpool256r1
Nbrainpool384r1
Nbrainpool512r1
Nfrp256v1
Nnumsp512d1
Nsecp192r1
Nsecp224r1
Nsecp256k1
Nsecp256r1
Nsecp384r1
Nsecp521r1
Nsm2p256v1
NPEM_Code
NPK_Ops
NPKCS11
NPKCS8
NPKIX
Nranges
NRoughtime
NSerpent_F
NSHA1_F
NSHACAL2_AVX2_F
NSHACAL2_AVX512_F
NSodium
NThreefish_F
NTLS
Ndetail
NInternal
NTPM2
Ndetail
NX509
NBotan_FFI