No, I haven't. I asked Apple support and they suggested turning off 'Search Engine Suggestions' and 'Safari Suggestions' in Safari preferences, and then clearing history and website data. The suggestions were gone at first, but reappeared after I visited a few websites.
I've tried various combinations of turning off the Safari settings above and the Siri settings that Rysz suggested, in combination with clearing history and website data. None had a long-term effect. The only way I've found to avoid them is to use Google Chrome instead of Safari, which I'm not too keen on.