To benefit the community, sharing the offline discussions.
Issue: Created Azure Cognitive Search instance (few days ago), and when running the query '*&speller=Lexicon', it throws an error: 'Parameter 'speller' is only supported for search services created on or after 2019-01-01'.
The availability of speller is inconsistent on free tier services. If you need to guarantee speller for your workloads, then it is recommended that you leverage basic tier or above services.
The Azure doc is now updated, to reflect that the Speller is supported in Basic tier and above : Add spell check - Azure Cognitive Search | Microsoft Learn: A search service at Basic tier or above, in any region
In addition, our product team is also reviewing to update the error message to add more clarity.
And you may post your suggestions and questions over the Azure community channel Azure Search · Community
@Vincent , Thanks again for your feedback on this and much appreciate your co-operation!