What is the point of enabling the "Use DNSSEC" option?

[jfb]

How do I interperet the DNSSEC column in the query log?

As of Pi-hole 3.3, you can see the DNSSEC status in the query log. [40] SECURE are records that have been signed and verified to be unchanged from the authoritative DNS server INSECURE are records that either have no signature or DNSSEC is not implemented for the domain; either the domain is unsigned and not implementing DNSSEC or there are other issues BOGUS are records that have been signed but have changed or been altered from the authoritative DNS server You will see INSECURE, but that …

It is normal (now) for most queries to show INSECURE, which indicates they don't have a DNSSEC record installed.