What's the oldest written publication that was written in a Native American language?
According to Britannica four codices exist.
Four codices are known to exist: the Dresden Codex, the Paris Codex, the Madrid Codex, and the Grolier Codex.
Dated to between the classic and conquest period
The codices are dated to between the classic and conquest period.
The set of year-bearers appearing in the codex offers a clue to the date of its production, placing it midway between the Classic and Conquest periods of Mayan history.
Just to give us an idea of when this period is, the classic period ends around the 10th century.
Maya hieroglyphs on stone and wood are confined largely to the Classic Period (300–900 CE),
The conquest period dates to the 16th century.
Paris Codex, Latin Codex Peresianus, one of the very few texts of the pre-Conquest Maya known to have survived the book burnings by the Spanish clergy during the 16th century
Madrid codex 1400ad
For a more precise estimate we can look at the Madrid codex which is estimated to have been written around 1400ad.
The Madrid Codex is believed to be a product of the late Mayan period (c. 1400 CE) and is possibly a post-Classic copy of Classic Mayan scholarship.
Oldest Native American written literature?
It appears to be either the Paris Codex written sometime between the 10th Century and 16th century, or the Madrid Codex, written approximately 1400ad, and thought to be a copy of earlier works