aarch64 support:
https://github.com/pocoproject/poco/commit/37899eda9563d9134cb5864751b6432cabfaac3e

riscv64 support:
https://github.com/pocoproject/poco/commit/26fa1b9e6bbe3a5d2d559d0e8bd5772a4e8fdfef

Index: Foundation/include/Poco/Platform.h
--- Foundation/include/Poco/Platform.h.orig
+++ Foundation/include/Poco/Platform.h
@@ -145,6 +145,8 @@
 #define POCO_ARCH_S390    0x0c
 #define POCO_ARCH_SH      0x0d
 #define POCO_ARCH_NIOS2   0x0e
+#define POCO_ARCH_AARCH64 0x0f
+#define POCO_ARCH_RISCV64 0x10
 
 
 #if defined(__ALPHA) || defined(__alpha) || defined(__alpha__) || defined(_M_ALPHA)
@@ -187,6 +189,9 @@
 	#else
 		#define POCO_ARCH_LITTLE_ENDIAN 1
 	#endif
+#elif defined(__AARCH64EL__)
+	#define POCO_ARCH POCO_ARCH_AARCH64
+	#define POCO_ARCH_LITTLE_ENDIAN 1
 #elif defined(__m68k__)
 	#define POCO_ARCH POCO_ARCH_M68K
 	#define POCO_ARCH_BIG_ENDIAN 1
@@ -208,6 +213,9 @@
 		#define POCO_ARCH_BIG_ENDIAN 1
 	#endif
 
+#elif defined(__riscv) && (__riscv_xlen == 64)
+	#define POCO_ARCH POCO_ARCH_RISCV64
+	#define POCO_ARCH_LITTLE_ENDIAN 1
 #endif
 
 
