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31 Upgrade notes for 6.4.21

Breaking changes

Java 11 required for Java gateway

Zabbix Java gateway now requires Java 11 for runtime (building from source is still possible with Java 8), due to updated minimum logback library versions:

Library New minimum version Old minimum version
logback-classic 1.5.16 1.2.9
logback-core 1.5.16 1.2.9
slf4j-api 2.0.16 1.7.32