Local Requirements
Use the local_requirements.txt file to install plugins for the update script. This is the proper way to do it as it is built in to the official update script and will run before doing the migrations.
nano /opt/netbox/local_requirements.txt
netbox-inventory==2.1.*
netbox-kea
netbox-device-view
netbox-metatype-importer
Update script
#!/bin/bash
cd /opt/netbox
sudo git fetch --tags
git describe --tags $(git rev-list --tags --max-count=1)
git checkout $(git rev-list --tags --max-count=1)
sudo ./upgrade.sh
sudo systemctl restart netbox netbox-rq