Noto emojis do not work in application title bars, and probably everywhere else in plasma workspace.
STEPS TO REPRODUCE
1. Install fonts-noto-color-emoji package.
2. Restart and observe.
Screenshot of its behavior in Chromium: https://i.fiery.me/7wit.png
* Title bar: some glyphs are missing, except scissor, and even then scissor is using black&white emoji (not sure from where it comes from, I do not have fonts-symbola package installed).
* Browser's tab bar and tooltip: missing glyphs are being fulfilled by noto emojis, but the existing scissor emoji keeps on using black&white.
* Browser's content (web page): noto emojis are all being used properly (at least from what can be seen from the scissor emoji).
On another note, firefox does not want to use noto emojis in its interface (browser tab and tooltip), however it does use them on web page: https://i.fiery.me/IZjR.png.
Only noto emojis being used everywhere.
KDE Plasma Version: 5.13.5
KDE Frameworks Version: 5.50.0
Qt Version: 5.11.1
I upgraded to bionic about a week ago, then a few days after I noticed that fonts-noto-color-emoji became a require dependency of neon-desktop. After installing it, they don't really work that well apparently.
*** This bug has been marked as a duplicate of bug 376813 ***