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