If anyone is
1) on Linux
2) using VSCodium
3) struggling to activate Synthwave '84 (https://github.com/robb0wen/synthwave-vscode)
You have to run the following command:
sudo chown -R (your local username):(your local username) /usr/share/codium/resources/app/out/vs/code/electron-browser/workbench
There's a file that needs to be written on a folder that's under the root user/group
