Developers have reported a significant increase of Applebot activity in their website, and speculate that a full-fledged search engine will be coming out soon.

Applebot is a web crawler to check how a website would rank depending on factors such as user engagement, how search terms match with content and topics, design characteristics and number of links.
The support document for Applebot has recently been updated in July 2020. Notable changes include traffic verification additions, an expanded robots.txt, a section that mentions how the engine renders pages like that of Google and factors affecting web search results, and expanded user agent details.
The idea that Apple is making its own search engine has been in circulation since 2015. However, it’s unlikely that the Cupertino-based company will be heading that route, and the recent activity suggests that Apple is working on improving Spotlight and Siri search results as mentioned in the updated Applebot support document.