Comment 3 for bug 1988055

I added the fix to a ppa and confirmed that the commit fixes the issue with a few additional modifications. If you would like to test it you can run the following commands in 22.04:

sudo add-apt-repository ppa:lvoytek/unbound-fix-checkconf-jammy
sudo apt update
sudo apt upgrade

I used the following test to confirm the fix:

# lxc launch images:ubuntu/jammy test-unbound
# lxc exec test-unbound bash

# apt update && apt dist-upgrade -y
# apt install unbound -y

# echo "
server:
  interface: lo" >> /etc/unbound/unbound.conf

# unbound-checkconf

- results in error: unbound-checkconf[871:0] fatal error: cannot parse interface specified as 'lo'

# lxc launch images:ubuntu/jammy test-unbound-fixed
# lxc exec test-unbound-fixed bash

# apt update && apt dist-upgrade -y
# apt install unbound software-properties-common -y

# add-apt-repository ppa:lvoytek/unbound-fix-checkconf-jammy
# apt update && apt upgrade -y

# echo "
server:
  interface: lo" >> /etc/unbound/unbound.conf

# unbound-checkconf