I did lots of searching and didn't find any command line terminal apps that support smooth scrolling. When you press up or down it just moves through lines with no transition in between lines.
Neovide is a very nice GUI for Neovim. When you move many lines down below the viewport, it scrolls smoothly as shown in the features page. Notice that it doesn't quickly move down individual lines to imitate true smooth scrolling. Unfortunately Neovide doesn't support tabs, and can't act as a pure terminal app (unless you want to run terminals inside Neovim), it was made specifically for Neovim.
Neovide is a very nice GUI for Neovim. When you move many lines down below the viewport, it scrolls smoothly as shown in the features page. Notice that it doesn't quickly move down individual lines to imitate true smooth scrolling. Unfortunately Neovide doesn't support tabs, and can't act as a pure terminal app (unless you want to run terminals inside Neovim), it was made specifically for Neovim.