According to my investigation,OpenJDK supports following CJK charsets:
(Mix means SBCS+DBCS, SB means SBCS Only, DB means DBCS Only)
Japanese EBCDIC - Katakana (Mix: 930, SB: 290, DB; 300)
Japanese EBCDIC - English (Mix: 939, DB: 300)
Korean EBCDIC (Mix: 933, SB: 833, DB: 83400
Simplified Chinese EBCDIC (Mix: 935)
Traditional Chinese EBCDIC (Mix: 937)
(Ref, https://www.ibm.com/docs/en/db2-for-zos/12?topic=identifiers-ebcdic-ascii-support )

Following charsets are missing
Japanese EBCDIC - English (SB: 1027)
Simplified Chinese EBCDIC (SB: 836, DB: 837)
Traditional Chinese EBCDIC (DB: 835)
*Note: Traditional Chinese EBCDIC 28709 is compatible with 037.
037 is supported by OpenJDK.

1027, 835, 836 and 837 may be required because of consistency.