The original post said "air gapped environments", not "air gapped computers". Running several computers on a network which has no connections to the outside qualifies as an air gapped environment, and will let you use a key server just fine.
My assumption is that the system is on an air-gapped network, as individual systems that are completely isolated are typically not very useful as a full user environment, and are more likely to be fully embedded systems instead.
That is not air gapped
The original post said "air gapped environments", not "air gapped computers". Running several computers on a network which has no connections to the outside qualifies as an air gapped environment, and will let you use a key server just fine.
My assumption is that the system is on an air-gapped network, as individual systems that are completely isolated are typically not very useful as a full user environment, and are more likely to be fully embedded systems instead.