MySQL 8.0 Release Notes
MySQL 8.0 Source Code Documentation
The Cyrillic character sets and collations are for use with Belarusian, Bulgarian, Russian, Ukrainian, and Serbian (Cyrillic) languages.
cp1251(Windows Cyrillic) collations:cp1251_bincp1251_bulgarian_cicp1251_general_ci(default)cp1251_general_cscp1251_ukrainian_ci
cp866(DOS Russian) collations:cp866_bincp866_general_ci(default)
koi8r(KOI8-R Relcom Russian) collations:koi8r_binkoi8r_general_ci(default)
koi8u(KOI8-U Ukrainian) collations:koi8u_binkoi8u_general_ci(default)