Search on the Rick Steves website is hiding in plain sight.
On a desktop or laptop (screen wider than it is tall): Find the dark blue Rick Steves Europe logo (top, to the left of center), and next to it, in the lightest possible type, is the Search box.
On a phone or tablet, or a browser window taller than it is wide: In the top left corner you will see horizontal lines. Click those, and the top option is the Search box.
You can also use Google search. To do this, put in your search terms (say, "gluten free Ireland"). You will get an avalanche of responses. Ignore these, and instead go to Settings at the top. Choose Advanced Search, and in the site or domain box put "ricksteves.com" to search the whole site, or "community.ricksteves.com" to search the forums (in both cases, without the quotation marks).