Problem
Qt-based applications will often display poor-quality, black and white emoji characters.
Cause
Qt does not recognize the ‘emoji’ generic font family, as defined in the W3C CSS Font Module standard. The way things should work is that Qt should look for the best implementation of the ‘emoji’ font family to display emoji characters (just as it would look for the best implementation of the ‘monospace’ family to display monospace text). This should result in it using the high-quality color renditions from the google-noto-emoji-color-fonts font, as we intend. However, Qt does not do this, so it instead winds up using lower-quality emoji renditions from a font that is marked as a member of the ‘serif’ family (Symbola).
Related Issues
Bugzilla report: #1954359
Upstream report: Qt #85744
Workarounds
You can save this file as /etc/fonts/conf.d/75-noto-color-emoji.conf to work around the problem. It would be best to remove it, or at least drop the section headed <!-- This adds Noto Color Emoji as a final fallback font for the default font families. -->, once a proper fix appears in Qt.