Hi @Misha Anker ,
Thanks for the additional info. Yes, SharePoint is supported for AI enrichment. To set up the SharePoint indexer, you'll need to perform some tasks in the Azure portal and others through the preview REST API. To accomplish this please see this document: https://learn.microsoft.com/en-us/azure/search/search-howto-index-sharepoint-online#functionality
Hope that helps.
It was just returning null, no other errors. After a bit of fiddling about with the context I was able to get one custom skill and one pre-written one working, but nothing using merged text, so i'm not sure if it's related to anything that doesn't use /document/content as its context?