Since the developers of VSCodium keep changing the icon, I've uploaded mine here, together with the svg and the size templates to re-create another one. That's it.
To change the icon on macOS
- open the Application folder on macOS
- click on the VSCodium.app and use File > Get Info
- drag the VSCodium.icns file from this repo to the VSCodium icon in the Get Info dialog
The previous icon will continue to show until macOS has updated its cache. Might take a reboot.