Log text garbled problem non UTF-8 "encoding" parameter in logrt[] key on Solaris11

Zabbix Server 5.0 (CentOS8.2/MySQL8)
Log history text was garbled from Solaris agents (encoding - shift_jis)

1. Agent 2.2.15 (Solaris11) => Server 2.2 - Japanese characters are OK.
2. Agent 2.2.15 (Solaris11)=> Server 5.0 - Japanese characters are garbled.
3. Agent 3.0.28 (Solaris11)=> Server 5.0 - Japanese characters are garbled.
4. Agent 4.0.1 (Solaris11)=> Server 5.0 - Japanese characters are OK.
5. Agent 5.0.3 (Solaris11)=> Server 5.0 - Japanese characters are OK.

Apply to customer's report and from our test we found that Japanese characters are garbled on Solaris system if using Zabbix Agent version below than 4.0(like 2.2 and 3.0) with Zabbix Server 5.0.
We think it may somehow the same with ZBX-15721.
Expected:
Japanese characters displayed normally