The issue is specific to particular websites where the touch action does not work. Some of the sites affected when clicking into an article:
bbc.co.uk/news
www.washingtonpost.com
www.cnn.com
www.scientificamerican.com


Manual selection of text does not work on any website. Click into an article on espn.com or nytimes.com and you can touch to search by tapping on a word, however, you cannot use the touch-and-hold gesture to manually select text (this is a feature that had worked since 2015: https://developers.google.com/web/updates/2015/10/tap-to-search).


I have the Pixel 2 on Oreo 8.1.0 and am using Chrome 66.0.3359.158.
- turning touch to search option off and on in settings did not help
- setting contextual search to "enable" in chrome://flags did not help
- clearing all chrome data from the app settings did not help
- uninstalling updates and using the default Chrome version 61.0.3163.98 on the Pixel 2 does work on all sites (it allows you to use the touch-and-hold gesture to manually select text, however, tap/touch-to-search does not work as it does in the newer versions of chrome)