Here are the portions of my unattend.xml file which are needed to turn on Remote Desktop automatically.

This piece flips the "no remote desktop" kill switch to "allow."

    <settings pass="specialize">
        ...
        <component name="Microsoft-Windows-TerminalServices-LocalSessionManager" ...>
            <fDenyTSConnections>false</fDenyTSConnections>

That's not enough; it is also necessary to poke a hole in the firewall to allow inbound connections.  I use an indirect string for the Group name, to allow for installing localized builds.  This points to the "Remote Desktop" feature group.

    <settings pass="specialize">
        ...
        <component name="Networking-MPSSVC-Svc" ...>
            <FirewallGroups>
                <FirewallGroup wcm:action="add" wcm:keyValue="RemoteDesktop">
                    <Active>true</Active>
                    <Profile>all</Profile>
                    <Group>@FirewallAPI.dll,-28752</Group>

If your user account is a member of the "Administrators" group, you're done:

    <settings pass="oobeSystem">
        <component name="Microsoft-Windows-Shell-Setup" ...>
            <UserAccounts>
                <LocalAccounts>
                    <LocalAccount wcm:action="add">
                        <Password>
                            <Value>#PASSWORD_ADMIN#</Value>
                            <PlainText>true</PlainText>
                        </Password>
                        <Name>Admin</Name>
                        <Group>Administrators</Group>

But if you're like me and you don't want to live in the Administrators group, you need to join the Remote Desktop Users group to be able to log in remotely:

    <settings pass="oobeSystem">
        <component name="Microsoft-Windows-Shell-Setup" ...>
            <UserAccounts>
                <DomainAccounts>
                    <DomainAccountList wcm:action="add">
                        <Domain>redmond.corp.microsoft.com</Domain>
                        <DomainAccount wcm:action="add">
                            <Group>RemoteDesktopUsers</Group>
                            <Name>MatEer</Name>