nut-scanner isn't required to set up TrueNAS with nut. Just makes picking the correct driver more of a pain.
That said, there appears to be a fix in nut that would allow nut-scanner to work with USB UPS devices. However, it's not until nut 2.8.0_4 and Core is still on 2.7.4_20, which is two years old at this point.
There's a ticket open to update nut to 2.8 but it was created in June and doesn't appear to have been looked at. https://ixsystems.atlassian.net/browse/NAS-122717
That said, there appears to be a fix in nut that would allow nut-scanner to work with USB UPS devices. However, it's not until nut 2.8.0_4 and Core is still on 2.7.4_20, which is two years old at this point.
There's a ticket open to update nut to 2.8 but it was created in June and doesn't appear to have been looked at. https://ixsystems.atlassian.net/browse/NAS-122717