https://www.gooksu.com/2022/01/esxi-7-x-nutclient-to-query-upsmon-on-synology/
Please download the latest NUT client from https://rene.margar.fr/2012/05/client-nut-pour-esxi-5-0/ I downloaded the file locally and scp the file to my ESXi host into /tmp/nut
uncompress the file
[root@localhost:/tmp/nut] tar -zxvf NutClient-ESXi-2.7.4-2.1.6.i386.tar.gz readme.txt upsmon-install.sh upsmon-remove.sh upsmon-update.sh upsmon-2.7.4-2.1.6.i386.vib
Install the client
chmod +x upsmon-install.sh ./upsmon-install.sh
Configure the service, log into your ESXi via the GUI and goto Manage → System → Advanced settings and look for UserVars.nut and update the values pending your settings