There's also an open source reimplementation of the original Gollop designed game which has extensive modding support. There's quite a few total conversion mods

There's also an open source reimplementation of the original Gollop designed game which has extensive modding support. There's quite a few total conversion mods for it https://openxcom.org/ https://openxcom.org/ https://mod.io/g/openxcom https://mod.io/g/openxcom