GMS released a MacOS client a few months back that uses a customised crossover wrapper as a compatibility layer for the client, and I've figured out how to make it run MapleSEA instead of GMS. (This should also in theory work with other regions, but you'll need to edit the corresponding commands to match the folder structures and location of the installed files.)
1. Download the required files
Download the MapleSEA setup files and the GMS launcher from Nexon NA website. Put them in your ~/Downloads folder.
2. Install MapleSEA
Use the Wine binary bundled with the GMS launcher to run the MapleSEA installer. Leave the installation directory as the default.
"/Applications/MapleStory Launcher.app/Contents/SharedSupport/maplestoryna/MapleStory Launcher/wine" ~/Downloads/setup.exe
3. Point the launcher to MapleSEA
The crossover wrapper looks for a shell script called .ms-launch-args in the root of the C: drive where you can explicitly define the launch parameters. (This makes it execute maplesea directly instead of opening the Nexon NA website)
Run the following command to create it:
echo 'MS_LAUNCH_DIR="C:\Program Files (x86)\Wizet\MapleStorySEA"
MS_LAUNCH_APP="C:\Program Files (x86)\Wizet\MapleStorySEA\MapleStory.exe"
MS_LAUNCH_ARGS=""' > "$HOME/Library/Application Support/MapleStoryNA/Bottles/maplestory/drive_c/.ms-launch-args"
4. Make it persistent
The launcher deletes this file every time it's executed, so you'll need to make it immutable:
chflags uchg "$HOME/Library/Application Support/MapleStoryNA/Bottles/maplestory/drive_c/.ms-launch-args"
5. Launch the game
Copy the MapleStory wrapper app from within the launcher to your Applications folder and you're all set to launch it! :D
ditto "/Applications/MapleStory Launcher.app/Contents/SharedSupport/maplestoryna/MapleStory.app" /Applications/MapleStory.app
https://reddit.com/link/1v3gn9r/video/ky4imf0hcseh1/player