Things I've learned building a modern TUI Framework (2022)

It's funny how every TUI developer eventually stumbles over Unicode and then handling international characters and emojis correctly turns into its own project close to the same scope of (or even bigger than) the original TUI project. It happened to me on rivo/tview and through the resulting rivo/uniseg package, I learned that all other TUI library maintainers deal with the same issues. Finally, everyone invents their own unique solutions to the problem because character width is not standardized and terminals are messy, as noted in the article. OP simply supports Unicode 9 only (Unicode is at version 15.1 at the moment). Sooner or later, users will complain, however, that certain emojis or international characters are not rendered correctly. So I'm not sure that this is a great solution.

Are there any libraries in place which can normalize all emojis down to a single symbol?

It doesn't matter; what matters is that both your (terminal-manipulating) program and terminal emulator agree on the symbols widths. Considering that they usually won't (lots of terminal emulators have their own hand-crafted, statically linked wcwidth/wcswidth functions; the readline library also has them hard-coded, by the way), it's quite frustrating.