It's a mix of Electron & native code (Swift). I have done so many optimizations to make it lightweight, smooth and fast. If you have an older Mac, try it on it and see how fast it is. I use Apple Mail app for my emails and for my benchmarks so far, Yack works faster and smoother than Apple Mail.
Give it a try and don't forget to report back here :)
It's really not. Even on my MacBook Air 2019 loading of the different communities is slow. Feedback for example at least takes 3,4,5 seconds. While Apple Mail is measurable in milliseconds.
Also when logging into hacker news it's loading an internal web view instead of a popup, a popup safari web view would be better because of password autofill.
Give it a try and don't forget to report back here :)