hello, i’m the original author of the Subnet Groups plugin: I wrote and committed the first version of its code back in 2019 (https://github.com/FOGProject/fogproject/pull/289).
i just wanted to inform you that in our environment (currently equipped with the last stable version of FOG) everything is working alright, we never had issues with the plugin even though we are used to update our systems on a regular basis.
as @Tom-Elliott mentioned, problems might arise due to incorrect IP addresses mapping: on our system, we had to set up a dynamic DNS server which has the job to automatically keep track of the actual host IPs based on their hostname; without this (or some alternative solution to correcly associate IPs with hosts) the plugin is not going to work properly.
best regards.