diff --git a/linux.md b/linux.md
index 1013f0b9..c1416611 100644
--- a/linux.md
+++ b/linux.md
@@ -35,13 +35,15 @@ Almost everything works, except the serial port.
 The UI has been rewritten in Qt or ImGui.
 
 The rest works very well.
-Uthernet is supported, but it requires elevated capabilities:
+Uthernet I is supported via `libpcap`, but it requires elevated capabilities:
 
 `sudo setcap cap_net_raw=ep ./sa2`
 
 Unfortunately, this must be reapplied after every build.
 
-Uthernet II is supported too (only MACRAW) and by default uses `libslirp` which does *not* require elevated capabilities. Use the ImGui settings to enable it.
+Uthernet II is supported too and by default uses `libslirp` which does *not* require elevated capabilities. Use the ImGui settings to enable it.
+
+`libslirp` is not packaged on Raspberry Pi OS. `libpcap` will be used instead, unless the user manually compiles and installs [libslirp](https://gitlab.freedesktop.org/slirp/libslirp).
 
 Most of the debugger now works (in the ImGui version).
 
diff --git a/source/CMakeLists.txt b/source/CMakeLists.txt
index dd4a2b91..faefae91 100644
--- a/source/CMakeLists.txt
+++ b/source/CMakeLists.txt
@@ -1,5 +1,33 @@
 include(FindPkgConfig)
 
+pkg_check_modules(YAML REQUIRED yaml-0.1)
+pkg_check_modules(MINIZIP REQUIRED minizip)
+pkg_check_modules(SLIRP slirp)
+
+if ("${SLIRP_FOUND}" STREQUAL "")
+  message(WARNING "'libslirp' not found. Will use 'libpcap' instead")
+endif()
+
+pkg_check_modules(PCAP libpcap)
+if ("${PCAP_FOUND}" STREQUAL "")
+  # old versions of pcap do not work with pkg-config
+  # this is necessary on Rapsberri Pi OS
+  execute_process(COMMAND pcap-config --cflags
+    OUTPUT_VARIABLE PCAP_INCLUDE_DIRS
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+    RESULT_VARIABLE STATUS)
+  if ("${STATUS}" STREQUAL "0")
+    message("Found 'libpcap' via pcap-config")
+  else()
+    message(FATAL_ERROR "Cannot locate 'libpcap-dev'")
+  endif()
+  execute_process(COMMAND pcap-config --libs
+    OUTPUT_VARIABLE PCAP_LIBRARIES
+    OUTPUT_STRIP_TRAILING_WHITESPACE)
+endif()
+
+find_package(Boost REQUIRED)
+
 set(SOURCE_FILES
   Tfe/tfe.cpp
   Tfe/tfearch.cpp
@@ -197,13 +225,8 @@ add_library(appleii SHARED
   ${HEADER_FILES}
   )
 
-pkg_check_modules(YAML REQUIRED yaml-0.1)
-pkg_check_modules(MINIZIP REQUIRED minizip)
-pkg_check_modules(PCAP REQUIRED libpcap)
-pkg_check_modules(SLIRP REQUIRED slirp)
-find_package(Boost REQUIRED)
-
 target_include_directories(appleii PRIVATE
+  ${CMAKE_CURRENT_BINARY_DIR}  # for config.h
   ${YAML_INCLUDE_DIRS}
   ${PCAP_INCLUDE_DIRS}
   ${Boost_INCLUDE_DIRS}
@@ -232,5 +255,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_SOURCE_DIR}/bin/*.SYM ${CMAKE_BINARY_DIR}
   )
 
+configure_file(linux/config.h.in linux/config.h)
+
 install(TARGETS appleii
   DESTINATION lib)
diff --git a/source/frontends/libretro/CMakeLists.txt b/source/frontends/libretro/CMakeLists.txt
index 750a6420..165879f4 100644
--- a/source/frontends/libretro/CMakeLists.txt
+++ b/source/frontends/libretro/CMakeLists.txt
@@ -48,5 +48,5 @@ if (EXISTS ${LIBRETRO_COMMON_PATH}/include/libretro.h)
   set_target_properties(applewin_libretro PROPERTIES PREFIX "")
 
 else()
-  message("Bad LIBRETRO_COMMON_PATH=${LIBRETRO_COMMON_PATH}, skipping libretro code")
+  message(WARNING "Bad LIBRETRO_COMMON_PATH=${LIBRETRO_COMMON_PATH}, skipping 'libretro' core")
 endif()
diff --git a/source/linux/config.h.in b/source/linux/config.h.in
new file mode 100644
index 00000000..d6fd654b
--- /dev/null
+++ b/source/linux/config.h.in
@@ -0,0 +1 @@
+#cmakedefine SLIRP_FOUND "@SLIRP_FOUND@"
diff --git a/source/linux/network/slirp2.cpp b/source/linux/network/slirp2.cpp
index 3ca17b1b..01d13085 100644
--- a/source/linux/network/slirp2.cpp
+++ b/source/linux/network/slirp2.cpp
@@ -1,12 +1,15 @@
 #include <StdAfx.h>
+
+#include "linux/network/slirp2.h"
+
+#ifdef U2_USE_SLIRP
+
 #include <libslirp.h>
 
 #include "Log.h"
 #include "CPU.h"
 #include "Core.h"
 
-#include "linux/network/slirp2.h"
-
 #define IP_PACK(a,b,c,d) htonl( ((a)<<24) | ((b)<<16) | ((c)<<8) | (d))
 
 namespace
@@ -179,3 +182,5 @@ void SlirpNet::clearQueue()
 {
   std::queue<std::vector<uint8_t>>().swap(myQueue);
 }
+
+#endif
diff --git a/source/linux/network/slirp2.h b/source/linux/network/slirp2.h
index 8eeb6f86..b4a89b34 100644
--- a/source/linux/network/slirp2.h
+++ b/source/linux/network/slirp2.h
@@ -1,4 +1,14 @@
 #pragma once
+
+#include "linux/config.h"
+
+#ifdef SLIRP_FOUND
+// disable to use libpcap in all cases
+#define U2_USE_SLIRP
+#endif
+
+#ifdef U2_USE_SLIRP
+
 #include <memory>
 #include <vector>
 #include <queue>
@@ -29,3 +39,5 @@ private:
 
   std::queue<std::vector<uint8_t>> myQueue;
 };
+
+#endif
diff --git a/source/linux/network/uthernet2.cpp b/source/linux/network/uthernet2.cpp
index d50979e1..5a241456 100644
--- a/source/linux/network/uthernet2.cpp
+++ b/source/linux/network/uthernet2.cpp
@@ -13,15 +13,12 @@
 // #define U2_LOG_STATE
 // #define U2_LOG_UNKNOWN
 
-// if this is defined, libslirp is used as opposed to libpcap
-#define U2_USE_SLIRP
-
 #include "linux/network/uthernet2.h"
 #include "linux/network/registers.h"
 
-#ifdef U2_USE_SLIRP
 #include "linux/network/slirp2.h"
-#else
+
+#ifndef U2_USE_SLIRP
 #include "linux/network/tfe2.h"
 #include "Tfe/tfe.h"
 #endif
@@ -570,7 +567,7 @@ namespace
     const int fd = socket(AF_INET, type | SOCK_NONBLOCK, protocol);
     if (fd < -1)
     {
-#ifdef U2_LOG_STATE      
+#ifdef U2_LOG_STATE
       const char * proto = state == SN_SR_SOCK_UDP ? "UDP" : "TCP";
       LogFileOutput("U2: %s[%d]: %s\n", proto, i, strerror(errno));
 #endif
@@ -608,7 +605,7 @@ namespace
 #endif
     }
     resetRXTXBuffers(i); // needed?
-#ifdef U2_LOG_STATE      
+#ifdef U2_LOG_STATE
     LogFileOutput("U2: OPEN[%d]: %02x\n", i, sr);
 #endif
   }
@@ -617,7 +614,7 @@ namespace
   {
     Socket & socket = sockets[i];
     socket.clearFD();
-#ifdef U2_LOG_STATE      
+#ifdef U2_LOG_STATE
     LogFileOutput("U2: CLOSE[%d]\n", i);
 #endif
   }