Ubuntu TC agent won't start "Unknown protocol: http2"

I started with Ubuntu 22.04 minimal install and have installed Docker. I then downloaded the buildagent zip file, set it up and tried to run `agent.sh start`

It goes through some motions but then errors out. The teamcity-agent.log ends with the following message. I suspect there is some package that would normally be installed on Ubuntu but I can't think what that would be.

[2022-11-23 11:39:50,409]  ERROR - s.buildServer.agent.AgentMain2 - Failed to start build agent. unknown protocol: http2

java.lang.RuntimeException: unknown protocol: http2
        at jetbrains.buildServer.xmlrpc.XmlRpcFactory.createCommonsHttpTransportTarget(XmlRpcFactory.java:85) ~[xml-rpc-wrapper.jar:?]
        at jetbrains.buildServer.xmlrpc.XmlRpcFactory.create(XmlRpcFactory.java:118) ~[xml-rpc-wrapper.jar:?]
        at jetbrains.buildServer.agent.impl.XmlRpcAgentLogListener.createTarget(XmlRpcAgentLogListener.java:60) ~[common-runtime.jar:?]
        at jetbrains.buildServer.agent.impl.XmlRpcAgentLogListener.<init>(XmlRpcAgentLogListener.java:56) ~[common-runtime.jar:?]
        at jetbrains.buildServer.agent.impl.XmlRpcAgentLogListener.<init>(XmlRpcAgentLogListener.java:45) ~[common-runtime.jar:?]
        at jetbrains.buildServer.agent.impl.ServerXmlRpcProxy.<init>(ServerXmlRpcProxy.java:44) ~[agent.jar:?]
        at jetbrains.buildServer.agent.impl.BuildAgentImpl.init(BuildAgentImpl.java:905) ~[agent.jar:?]
        at jetbrains.buildServer.agent.AgentMain2.startAgent(AgentMain2.java:216) ~[agent.jar:?]
        at jetbrains.buildServer.agent.AgentMain2.main2(AgentMain2.java:92) ~[agent.jar:?]
        at jetbrains.buildServer.agent.AgentMain2.main(AgentMain2.java:39) ~[agent.jar:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_352]
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_352]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_352]
        at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_352]
        at jetbrains.buildServer.agent.AgentMain.main(AgentMain.java:43) ~[agent.jar:?]
[2022-11-23 11:39:50,414]   INFO - ent.impl.upgrade.AgentExitCode - Agent exited. Failed to start build agent