Can iOS spell checker auto detect which language is being used?

AirpodProRecall wrote:

Can iOS spell checker auto detect which language is being used?

For some languages I think yes

iOS and iPadOS - Feature Availability - Apple

AirpodProRecall wrote:

Can iOS spell checker auto detect which language is being used?

With English and Español (México) including mixed text, when the languages are configured, yes.

I'd expect other languages will work, as well.

See Settings > General > Keyboard, and Settings > General > Language & Region

Predictive texts yes.