@Tsudow
By the promo videos, they should adapt it until events after Osterd incident, or more exactly until Eris depart and the end of the journey Arc.
25 episodes, 2 chapters by episode using the manga as measurement, would do the job.
Although by the VA casting announced, the absence of Ruijerd may be an indicator of a 12 episodes season (and God knows if in the case the second season would come also in 2021).
But for a 12 episode seadon, the ending or would be a cliffhanger of hell, right after the teleport, what is bad because you finish episodes with cliffhangers, not seasons... Or they just will introduce Ruijerd but finish it before they met tbe Roxy's parents village.