So... is Uchuu Taitei God Sigma finished or not?
NO, it is not finished.
Why?
MangaUpdates contains information about the anime adaptation and indicates that it is incomplete.
Watching Order (by release date)
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Synopsis
In the year 2050, humanity's space exploration is threatened by the arrival of the Eldar, a force from the future. They seek to prevent Earth from developing a powerful energy source called Trinity Energy.
The Eldar, fearing Earth's future dominance, launch attacks on human settlements, starting with Io, a moon of Jupiter. Their goal is to steal the Trinity Energy before it can be used against them.
Humanity's defense rests on the shoulders of Toshiya and his comrades, who pilot God Sigma. They engage in a desperate battle to protect Earth and its powerful energy source from the invading Eldar forces, leading to a prolonged conflict.