Not sure what is going on with those URL params, but I see results just fine at https://duckduckgo.com/?q=site%3Atass.com and in any case an easier way to do things is to not use a site search but just put the domain or name in the query like 'ukraine tass' and something from that site will usually come up on top.
The same people that would complain about "death panels" in a public health care system seem awfully eager to toss people in their 20s and 30s into the pit.