The newest version of Unicode is Unicode 13.0.0 since about one year (see http://www.unicode.org/versions/Unicode13.0.0/). We should finally update Ruby to use Unicode 13.0.0, and probably also backport the result to Ruby 3.0. This issue serves as the main issue for this update; if necessary, I'll create sub-issues.
Currently, I don't expect any major issues (stuff that would require rewriting code) for this upgrade, but I'll check again carefully.
One problem I know of is that Unicode changed the structure of their directories somewhat. This may affect the Ruby makefile infrastructure.
The two files emoji-data.txt and emoji-variation-sequences.txt move from https://www.unicode.org/Public/emoji/12.1/ in Emoji version 12.1 to https://www.unicode.org/Public/13.0.0/ucd/emoji/ in Unicode Version 13.0.0.
We will reflect this in also changing the location of the files when building Ruby.
To get all the files, use
$> make update-unicode
In some cases, it will be necessary to temporarily uncomment the following line in common.mk: # ALWAYS_UPDATE_UNICODE = yes
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