Elasticsearch engine versions (i.e. not OpenSearch) seem to be no longer available when creating a domain

Does anyone know if support for elasticsearch versions (e.g. 5.6 or 6.8) has been recently discontinued? I.e. are only OpenSearch versions supported.

We are in the progress of updating an older domain, running elasticsearch 5.1 and last week in our staging account, I create a domain running 6.8, installed the indices from snapshot, reindexed and modify them to be compatible with version 7.10 ( and thereby OpenSearch) and upgraded that domain to 7.10. But when I then tried to reindex directly from the original 5.1 domain to get updates, there were version issues, so basically we need to reindex first to 6.x and then to 7.x or OpenSearch domains. But when I wanted to create a temporary domain with version 6.8, to do the "in between" reindexing, the only options for engine version seem to be for OpenSearch versions. So has this been changed since last week?!