RxJava instrumentation not working via auto configuration

RxJava app does not send any trace to Jaeger automatically. It only works using a manual Tracer Configuration and wrapping the subscribers and observers in the Tracer decorators (like in this app).

Please see this stackoverflow question for details.

Is this expected? Shouldn't it work automatically without having to configure a Tracer bean?

Below is my pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
		 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.3.1.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example.springcloud</groupId>
	<artifactId>rxjava</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>rxjava</name>
	<description>RxJava Spring Cloud</description>

	<properties>
		<java.version>11</java.version>
		<spring-cloud.version>Hoxton.SR6</spring-cloud.version>
	</properties>
	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>${spring-cloud.version}</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>io.opentracing.contrib</groupId>
			<artifactId>opentracing-spring-jaeger-cloud-starter</artifactId>
			<version>3.2.0</version>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-webflux</artifactId>
			<version>2.3.4.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>io.reactivex</groupId>
			<artifactId>rxjava</artifactId>
			<version>1.3.8</version>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>

Start with the supplied pom.xml and compare the RxJava 1.3.8 and opentracing-spring-jaeger-cloud-starter 3.2.0 setup with the manual Tracer Configuration and decorator usage described in the issue. Read the linked Stack Overflow question and example application first; done means determining whether automatic tracing is expected for this configuration and documenting the observed behavior.