I needed a version in addition to classifier:
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-resolver-dns-native-macos</artifactId>
<scope>runtime</scope>
<classifier>osx-x86_64</classifier>
<version>4.1.59.Final</version>
</dependency>
scope is optional but classifier is required.
For the latest version, see:
https://mvnrepository.com/artifact/io.netty/netty-resolver-dns-native-macos
Example: Latest version for M1 macs (aarch_64), as of 2022-01:
<classifier>osx-aarch_64</classifier>
<version>4.1.72.Final</version>