It seems that the Netty version comes together with
org.apache.camel.springboot:camel-spring-boot-starter:jar:3.4.0
--> org.springframework.boot:spring-boot-starter:2.3.0.RELEASE
--> org.springframework.boot:spring-boot-dependencies:2.3.0.RELEASE
--> io.netty:netty-bom:4.1.49.Final