Ubuntu update to isc-dhcp-server seems to have broken config file processing

[bls s]

I'm using isc-dhcp-server 4.4.1-2 on RasPiOS Buster, and it's working fine with the following subnet declaration:

subnet 192.168.92.0 netmask 255.255.255.0 {
    option domain-search "foo.com", "dyn.foo.com";
    option broadcast-address 192.168.92.255;
    allow duplicates;
    ddns-updates off;
    pool {
        ddns-updates on;
        allow unknown-clients;
        option domain-name "dyn.foo.com";
        ddns-rev-domainname "dhcp";
        default-lease-time 86400;
        max-lease-time 86400;
        range 192.168.92.101 192.168.92.127;
    }
}

This same subnet config worked on Ubuntu 21.04 a couple of weeks ago, with isc-dhcp-server V4.4.1-2.2-ubuntu6 on it. Today I updated on Ubuntu, got isc-dhcp-server V4.4.1-2.2ubuntu6.1 and now isc-dhcp-server complains about "Can't clone pool group".

I found that I can put the pool declaration outside of the subnet declaration on Ubuntu, and it works correctly. Unfortunately, doing this on RasPiOS fails!

Am I totally using subnet and pool incorrectly, or is this an incompatible change in isc-dhcp-server? And, is it an intended change coming to mainline isc-dhcp-server or did Ubuntu bork it?

This is important (to me, anyhow), since I have a tool that automatically builds dhcpd.conf from a database, and now it's broken with no easy way to fix other than putting in "do it this way/that way" switches.

Thanks for your help!

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