“dig +trace” to Unbound doesn’t work for long time due to RD=0 queries for root server (we often need “allow_snoop” access-control to accept them). Now ISC fixed this issue (BIND 9.11.8)
https://gitlab.isc.org/isc-projects/bind9/commit/7575b663ad1697c03b1efa5f08d5617532128f6f
