Use this userscript if you see black box (missing glyphs) instead of emojis on your favorite sites.

Originally made for use with this font (instead of system Windows 10 font ­­— Segoe UI Emoji):
https://github.com/googlefonts/noto-emoji/blob/master/fonts/NotoColorEmoji_WindowsCompatible.ttf
(to work properly, you must first install this font ↑)
but you can edit it for yourself (via adding other Emoji fonts: it is not recommended to add Last Resort fallback-font, because it can interfere with non-Emoji special characters rendering).

Script based on:
https://gist.github.com/mienaikage/4f487dcee7d04ba2f6d4c615812af668

Warning: the script can be very resource-intensive for your use case!