Here is a list of all namespaces with brief descriptions:

NBotan
NAES_AARCH64
NARIA_AVX512
NARIA_F
NARIA_HWAES
NASN1
NCamellia_AVX2_GFNI
NCamellia_AVX512
NCamellia_F
NCamellia_HWAES
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
NSEED_AVX512_GFNI
NSEED_HWAES
NSerpent_F
NSHA1_F
NSHA512_AVX512
NSHACAL2_AVX2_F
NSHACAL2_AVX512_F
NSM4_AVX512_GFNI
NSodium
NThreefish_F
NTLS
Ndetail
NInternal
NTPM2
Ndetail
NTwofish_AVX512
NTwofish_KS
NWhirlpoolAVX2
NWhirlpoolAVX512
NX509
NBotan_FFI