diff --git a/.gitmodules b/.gitmodules
index 10575207..08b94c96 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,7 +1,7 @@
 [submodule "depends/libnbtplusplus"]
     path = libraries/libnbtplusplus
-    url = https://github.com/MultiMC/libnbtplusplus.git
-    pushurl = git@github.com:MultiMC/libnbtplusplus.git
+    url = https://github.com/PolyMC/libnbtplusplus.git
+    pushurl = git@github.com:PolyMC/libnbtplusplus.git
 
 [submodule "libraries/quazip"]
 	path = libraries/quazip
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7537703c..889d6fc4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.9.4)
 
 if(WIN32)
     # In Qt 5.1+ we have our own main() function, don't autolink to qtmain on Windows
@@ -43,6 +43,18 @@ set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -Werror=return-type")
 # Fix build with Qt 5.13
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DQT_NO_DEPRECATED_WARNINGS=Y")
 
+include(CheckIPOSupported)
+check_ipo_supported(RESULT ipo_supported OUTPUT ipo_error)
+
+if(ipo_supported AND (CMAKE_BUILD_TYPE STREQUAL "Release" OR CMAKE_BUILD_TYPE STREQUAL "MinSizeRel"))
+    message(STATUS "IPO / LTO enabled")
+    set(CMAKE_INTERPROCEDURAL_OPTIMIZATION TRUE)
+elseif(ipo_supported)
+    message(STATUS "Not enabling IPO / LTO on debug builds")
+else()
+    message(STATUS "IPO / LTO not supported: <${ipo_error}>")
+endif()
+
 ##################################### Set Application options #####################################
 
 ######## Set URLs ########
diff --git a/libraries/LocalPeer/CMakeLists.txt b/libraries/LocalPeer/CMakeLists.txt
index 1e7557ec..0b434803 100644
--- a/libraries/LocalPeer/CMakeLists.txt
+++ b/libraries/LocalPeer/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.9.4)
 project(LocalPeer)
 
 find_package(Qt5 COMPONENTS Core Network REQUIRED)
diff --git a/libraries/iconfix/CMakeLists.txt b/libraries/iconfix/CMakeLists.txt
index 049879c4..08441203 100644
--- a/libraries/iconfix/CMakeLists.txt
+++ b/libraries/iconfix/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.9.4)
 project(iconfix)
 
 find_package(Qt5Core REQUIRED QUIET)
diff --git a/libraries/javacheck/CMakeLists.txt b/libraries/javacheck/CMakeLists.txt
index f599bf15..735de443 100644
--- a/libraries/javacheck/CMakeLists.txt
+++ b/libraries/javacheck/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.9.4)
 project(launcher Java)
 find_package(Java 1.7 REQUIRED COMPONENTS Development)
 
diff --git a/libraries/katabasis/CMakeLists.txt b/libraries/katabasis/CMakeLists.txt
index d579dc29..77db286a 100644
--- a/libraries/katabasis/CMakeLists.txt
+++ b/libraries/katabasis/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.6)
+cmake_minimum_required(VERSION 3.9.4)
 
 string(COMPARE EQUAL "${CMAKE_SOURCE_DIR}" "${CMAKE_BUILD_DIR}" IS_IN_SOURCE_BUILD)
 if(IS_IN_SOURCE_BUILD)
diff --git a/libraries/launcher/CMakeLists.txt b/libraries/launcher/CMakeLists.txt
index 54913fd4..0eccae8b 100644
--- a/libraries/launcher/CMakeLists.txt
+++ b/libraries/launcher/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.9.4)
 project(launcher Java)
 find_package(Java 1.7 REQUIRED COMPONENTS Development)
 
diff --git a/libraries/libnbtplusplus b/libraries/libnbtplusplus
index dc72a20b..b156bcaa 160000
--- a/libraries/libnbtplusplus
+++ b/libraries/libnbtplusplus
@@ -1 +1 @@
-Subproject commit dc72a20b7efd304d12af2025223fad07b4b78464
+Subproject commit b156bcaa4acf0a5b392bbed60bd274c39e2398d4
diff --git a/libraries/optional-bare/CMakeLists.txt b/libraries/optional-bare/CMakeLists.txt
index b8b498c5..952df6e2 100644
--- a/libraries/optional-bare/CMakeLists.txt
+++ b/libraries/optional-bare/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.9.4)
 project(optional-bare)
 
 add_library(optional-bare INTERFACE)
diff --git a/libraries/rainbow/CMakeLists.txt b/libraries/rainbow/CMakeLists.txt
index e57dbbc2..94cc1b49 100644
--- a/libraries/rainbow/CMakeLists.txt
+++ b/libraries/rainbow/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.9.4)
 project(rainbow)
 
 find_package(Qt5Core REQUIRED QUIET)
diff --git a/libraries/xz-embedded/CMakeLists.txt b/libraries/xz-embedded/CMakeLists.txt
index 86ac60c8..4ce46102 100644
--- a/libraries/xz-embedded/CMakeLists.txt
+++ b/libraries/xz-embedded/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.9.4)
 project(xz-embedded LANGUAGES C)
 
 option(XZ_BUILD_BCJ "Build xz-embedded with BCJ support (native binary optimization)" OFF)