Dist of Columbia
The rules for solo play are for a cooperative game in which you play with all the tribes. Has anybody tried to play with a single tribe?
Playing with all the tribes feels less thematic and more complex. A variant in which you had random attacks and extinction of biomes due to the other tribes would be great!
For an engaging competitive solo experience try the Frozen Valhalla variant, by NoppaGames. While it is still a work in progress, it succeeds IMHO in restoring part the adversarial and competitive nature of multiplayer Greenland.