I was used to the bangs in DuckDuckGo too, but stopped using them. In example I have duckduckgo search engine disabled here, but can still do a ddg only search with !ddg hello . But don't get your hopes too high, because I think it only supports the few bangs and nothing else. It does not support ddg bangs. I registered a DuckDuckGo bang !retro to point to RetroPie forum, but it does not work in Searx.
Edit: It would have been a true banger if we could combine them in Searx like this: !ddg!retro