I personally never used this Search Engine. If it is a local project where the DuckDuckGo search engine is used will help you to get a little push in traffic. DuckDuckGo is mostly used in Austria, Belgium, Bulgaria, Croatia, Czech Republic, Denmark, France, Finland etc. The people who used it are those who already know about it. Approx 93% of people directly access the websites on it and only 1.5% of traffic comes through organic searches. So, it is up to you whether it's a great choice or not to optimize for DuckDuckGo. Curious to know the opinions of expert Digital Marketers.
Do we need to submit sites to search engines these days? I believe all of them crawl and get the site indexed whether we need it or not