• Use GModCEFCodecFix[github.com], it fixes codecs and the crashing issue
  Note: If you replaced Chromium libraries in the past, restore the ones provided by the game
  
• Link global Chromium libraries (any flavour)
  
  1. Back up existing libraries
     
     mv /path/to/GarrysMod/bin/linux64/libGLESv2.so{,.bak} mv /path/to/GarrysMod/bin/linux64/libEGL.so{,.bak}
  2. Link global libraries to game library path
     
     ln -s /usr/lib/chromium/{libGLESv2,libEGL}.so /path/to/GarrysMod/bin/linux64/

1. Back up the original menu
   
   mv /path/to/GarrysMod/garrysmod/lua/menu/menu.lua{,.bak}
2. Clone gmod-lua-menu someplace else
   
   cd /tmp/ git clone https://github.com/robotboy655/gmod-lua-menu
3. Copy materials and lua directories over to the game installation
   
   cp -r gmod-lua-menu/{materials,lua} /path/to/GarrysMod/garrysmod/

1. Obtain OpenSSL 1.0.1u[www.openssl.org]
   
2. Extract the archive and compile it
   
   tar xzf openssl-1.0.1u.tar.gz cd openssl-1.0.1u ./config shared make -j$(nproc)
3. Copy the compiled libraries to your game installation
   
   cp {libssl,libcrypto}.so* /path/to/GarrysMod/bin/linux64

• Substitute the file paths of both .res files with GarrysMod/garrysmod/, and replace both of them. Note file capitalisation differences
  
• The Missing Glyphs section is redundant until "SetLocale('en_US.UTF-8') failed" is fixed

SetLocale('en_US.UTF-8') failed. Using 'LC_CTYPE=en_US.UTF-8;LC_NUMERIC=C;LC_TIME=en_US.UTF-8;LC_COLLATE=en_US.UTF-8;LC_MONETARY=en_US.UTF-8;LC_MESSAGES=en_US.UTF-8;LC_PAPER=en_US.UTF-8;LC_NAME=en_US.UTF-8;LC_ADDRESS=en_US.UTF-8;LC_TELEPHONE=en_US.UTF-8;LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=en_US.UTF-8'.
You may have limited glyph support.
Please install 'en_US.UTF-8' locale.

• AppFramework : Unable to load module engine_client.so | Issue #5056[github.com]
  
• Game crash on Steam Linux Runtime | Issue #5092[github.com]
  
• Startup Crash on Linux | Issue #5096[github.com]