Are Talenta Halflings (Eberron) a selectable race within the DnDBeyond Character Creation App? I'm not seeing that specific race in the Eberron online source books and I'm reluctant to buy them unless one of those sources has the Talenta Halfling. I have most of the "basic" source books for 5e.

There is about 4 paragraphs of text for the Talenta Halflings specifically in Eberron: Rising from the Last War. There isn't a selectable subrace for Talenta Halflings however, as the Halflings of Eberron are described as such according to the aforementioned book.

The halflings of Eberron originate from eastern Khorvaire, and many nomadic tribes of halflings still travel the Talenta Plains. The appearance of dragonmarks among the halflings spurred their slow migration across Khorvaire, spreading their services of healing and hospitality along with the migration of the earliest humans across the continent. Now they are found in every part of Khorvaire, putting their distinctive talents to use.

Lightfoot halflings are the more widespread halfling subrace, especially in the Talenta Plains, but stout halflings are found within nearly every halfling community.

Sorry if that isn't what you're hoping for, but mechanically Talenta Halflings according to 5e are the same as Lightfoot/Stout Halflings as described in the PHB.

A non-dragonmarked halfling has the same stats as a regular halfling (stout or lightfoot).

Eberron adds two dragonmarked variants, Mark of Healing and Mark of Hospitality.