heftig

It’s neither. There are no voxels. Maybe “polygon creatures”.

I would add the 1999 game Warzone 2100 to this list. Much like Earth 2150 you can design your own units and it also has the persistent homebase + mission outposts system. It was open-sourced in 2004 and has received quite a bit of love since then.

I’ve tried, but Signal is just too cumbersome to use. I sorely miss a web client and my family members sorely miss an Android tablet client. This makes it hard to recommend.