Comment 12 for bug 1876034

The fix works for me. It's relatively easy to check for yourself with Docker.

To reproduce the issue (version 20.04.4):
docker run --rm ubuntu:focal bash -c 'export DEBIAN_FRONTEND=noninteractive && apt-get update && apt-get -y install --no-install-recommends command-not-found && apt-get update ; apt-cache policy command-not-found'

To test the fix (version 20.04.5):
docker run --rm ubuntu:focal bash -c 'echo "deb http://archive.ubuntu.com/ubuntu/ focal-proposed restricted main multiverse universe" > /etc/apt/sources.list.d/ubuntu-focal-proposed.list && export DEBIAN_FRONTEND=noninteractive && apt-get update && apt-get -y install --no-install-recommends command-not-found && apt-get update ; apt-cache policy command-not-found'