There isn't a way to do that without exposing the contents of the article publicly. That's why a lot of article paywalled sites can actually be accessed by just turning JavaScript off as they're just hiding the article with JavaScript and CSS or by switching browser agent to act like they're a Google crawler.
The best way to have your articles accurately indexed is to use SEO methods like JSON-LD structured data (Schema), which is built into Joomla 5. There you can describe exactly what the article is about. This would avoid exposing your articles for the purpose of crawling.
We've also released a plugin to take SEO to the next level and bring Joomla 5's Schema support to Joomla menu items so you can have solid SEO no matter the page. CB SEO also implements OpenGraph so when your website is shared on social media you can have the image you want and the text you want displayed properly.
www.joomlapolis.com/addons/cb-seo