The micrometer extension isn't listed here:

https://github.com/wildfly/wildfly/blob/34.0.0.Final/galleon-pack/galleon-feature-pack/wildfly-feature-pack-build.xml#L93-L106

This means galleon doesn't generate features for the micrometer resources, which means its resources can't be used in a provisioning.xml to provision a custom domain config.

That's very much a corner case, so I've filed this as minor. The main significance of this is just to help in a tiny way to avoid confusion that this extension can't work in a domain. It can, and does; just run the OOTB domain.sh and...

/extension=org.wildfly.extension.micrometer:add
/profile=full/subsystem=micrometer:add(endpoint=http://localhost:4318/v1/metrics,exposed-subsystems=[*])
reload --host=primary

Have a look at $WILDFLY_HOME/domain/servers/server-one/log/server.log and you'll see it complaining about not being able to connect the the non-existent collector, same as a standalone server would.