LDML keyboard mappings for XKB layouts.
Unicode’s Common Locale Data Repository (CLDR) collects locale data for all countries and languages, including keyboard layouts in LDML format. In particular, there are some useful charts. These cover Windows, Mac, Android and Chrome OS layouts, but are missing Linux layouts.
I generated LDML and charts for Linux from xkeyboard-config (commit 297bb515):
xkbcli list > xkbcli-list.yaml
python3 xkb_ldml.py
Download CLDR data and tools from http://cldr.unicode.org/index/downloads . Extract data.
java -DCLDR_DIR=cldr -DCLDR_TMP_DIR=tmp -jar cldr-tools-40.0.jar showkeyboards