I guess I haven't really needed to find a new macOS Twitter client lately, but upon updating my home computers to High Sierra (finally), I found that the Tweetdeck macOS app doesn't really play nice with it. There's still the Tweetdeck web interface, but that lives in a browser and the way I use my browser on my computers, I can't really have Twitter hidden and buried underneath all my other tabs.
So I went in search of a new alternative. I almost paid for Tweetbot for Mac, and then at the last moment, I discovered Tweeten. Tweeten is based off of Tweetdeck which explains the familiar layout and most of the keyboard shortcuts are the same. There are a few improvements in Tweeten, like layout, account handling, and DM handling, and overall I think it's a solid FREE alternative to the official Twitter app. Tweetdeck users will feel right at home.