Full disclosure, I haven't seen the movie yet, so I can't comment on the specifics of the film (like if the geography looks like the Dakotas or Montana), but I can provide some context for the Comanche/French interactions in the early 1700s.

First, and this seems silly to say but necessary, the interior of North America was a highly dynamic place with nations contracting and expanding, coalescing, and migrating in and out constantly. The Comanche themselves originated in the area we now call Wyoming in the 1600s when a group of Eastern Shoshone migrated east onto the Plains. They weren't the first to take this route, the Apache and Navajo likewise migrated to the Southwest slightly earlier, and they wouldn't be the last as eastern tribes displaced by European expansion sought a new life in the interior. I know you likely didn't mean anything by the word choice, but I would avoid saying they were "wandering". Migrations occur for a wide variety of push/pull factors, and several sources mention the Comanche were intentionally seeking out better access to resources, specifically horses coming out of New Mexico, instead of aimlessly moving about the landscape.

The French founded New Orleans in 1718 and given the pressure of Spanish and English/American interests, quickly needed to uncover the geography of the interior as it relates to the Mississippi watershed. Jean-Baptiste Benard de La Harpe left New Orleans with specific instructions to establish trade with indigenous nations and the Spanish in New Mexico, discover the sources of the Red and Arkansas Rivers, and lay claim to French territory. La Harpe traveled up the Red River in 1718, meeting with the Natchez and Caddo, and exchanging squabbling letters with New Mexico about territorial claims. This initial expedition was followed up in 1721 through Texas, where La Harpe was arrested by the Spanish for "inciting Indians against Spain". Fur trappers don't often show up in the documentary record, and usually range far in advance of official expeditions, but we have at least these two instances of French expansion into Comanche area, or at least soon to be Comanche area, in the early 1720s.

The Comanches migrated south into the heartland of the southern Plains, and effectively blocked France from accessing New Mexico, just as they blocked Spanish efforts to expand out of the Rio Grande area. They pushed the Apaches out of the Red River area by the 1720s, with Apaches reporting to a Spanish office about extensive Comanche raiding of their rancherias in 1723. The Comanches continued to expand, and cemented their role as middle men in the trade networks of the Southern Plains. They were regular attendees at trade fairs in Taos, preferring to avoid the Apache-dominant trade fair at Pecos, and then went east to trade with Louisiana, typically through the Wichitas. They traded horses, mules, and slaves for guns, metalware, and carbohydrates like corn to supplement their meat-rich diet. Spain officially prohibited selling firearms to indigenous peoples, but with access to French guns we have reports of the Comanche selling French firearms to the Spanish in New Mexico.

So, not knowing what the environment looked like in the film, we can still say it is highly possible to have French interaction with Comanches by the 1720s at the absolute latest in the area of the Red River or Texas.

For more info

Calloway One Vast Winter Count: The Native American West Before Lewis and Clark

Hämäläinen The Comanche Empire

Kavanagh The Comanches: A History, 1706-1875

Follow-up question: in the movie, the protagonist spoke English but not French. Is it realistic for a Comanche person to know English? Is it realistic for a Comanche person to know English but not know French?