What does cat /etc/resolv.conf tells you?
I figured it out. The locale needs to be set for Bullseye before installing Docker.
I followed the instructions from this Serverfault answer including a comment that says to run update-locale LANG=en_US.utf8.
Err… I wonder how you linked that error message to a locale problem 
I am having the same issue and don’t know too much about docker and settings Locales.
However I followed the instructions in the link but still no luck…
Did you need to uninstall Docker and OS Agent,
then set the Locale,
then reinstall Docker, OS Agent and homeassistant-supervised.deb?
You need to set the locale first and then reboot before installing Docker. That’s what worked for me.
Also, I think running apt upgrade at the moment will cause the HA install to crash Debian. Need to validate this further, but have not had time.
you can try my scripts to help you install it.
you can find it GitHub - tirtadji-com/rpi_debian_ha_supervised: Installation for official Debian running Home-Assistant Supervised
I came across this thread looking for a solution for the same error and solved it in a more radical way…
Was installing a fresh Debian 11 on my server and no matter what I was unable to download the containers (but hello world container downloads and run just fine):
--- version.home-assistant.io ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 30.098/30.098/30.098/0.000 ms
[info] Install supervisor Docker container
Error response from daemon: Get "https://registry-1.docker.io/v2/": dial tcp: lookup registry-1.docker.io on [::1]:53: read udp [::1]:60704->[::1]:53: read: connection refused
dpkg: error processing package homeassistant-supervised (--install):
installed homeassistant-supervised package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
homeassistant-supervised
The error is probably related to DNS but even installing resolve.conf as service and set my DNS nameservers permanent dpkg/docker refused to install the containers.
Lucky me, I still had a copy of Buster’s iso… I’ve installed it again, did a complete installation process for the supervisor with no errors and then I’ve updated the distro to Bullseye.
All it had taken was 20-25 more minutes including merging my HA backup and now all is updated and is working fine.
F.
Has anyone else been able to fix this issue?
I tried reconfiguring the locale and even the installed Debian using us UTF 8 as the main locale but no luck.
It seems to be an issue with the installation script trying to use IPv6 DNS to resolve to the docker.io address.
Lol, yeah I was trying to avoid that.
It is my last resort option. I’m migrating from a raspberry to a mini pc so I’m not in a hurry. I’ll give it a few more tries before I give up.
Proxmox that PC and decouple everything. 
Ok, for future reference. I did a few changes before installing Docker:
- Fresh Debian 11 install
- Disabled IPv6 from my network
- Used the instructions here to set resolv.conf Bug Report: Can't install homeassistant-supervised.deb - issue Hi,Github
- Reboot
- Followed steps from the supervised installation up to before running homeassistant-supervised.deb (another reboot just in case)
- Run Docker pull homeassistant/amd64-hassio-supervisor:latest
- Run dpkg -i homeassistant-supervised.deb
- Cross fingers
That worked for me!!
2 Likes
All this did not help.
Found a simple workaround.
Edit /etc/hosts and add
140.82.121.34 ghcr.io
185.199.108.154 pkg-containers.githubusercontent.com
etc.
3 Likes
This works for me, issue was registry-1.docker.io not resolving in IPv6
34.203.135.183 registry-1.docker.io
140.82.121.34 ghcr.io
Stared at it for a couple of days, searched for a solution a couple of days, but answer was right in front of me the whole time 
Anoyher and probably more viable solution than the above workaround (ip addresses can change at any time) can be found here.
Hello, Just tried the installation of home assistant supervised on Debian 11 Bullseye myself.
I tried now several times, but dns seems to fail after the home assistant supervised installation.
Somehow it will not connect to the local DNS server. (which in my case it recieves from DHCP. )
To overcome that I added now the google DNS servers (with the procedure above).
sudo nmcli connection modify "Supervisor eth0" ipv4.dns "8.8.8.8"
Remote DHCP now seems to work for the external URLs. However, my esphome boards are not reachable due to a failing dns request (The requests were working before the home assisstant supervised installation)
Checking the /etc/resolv.conf however shows the local DNS server as being configured:
$ more /etc/resolv.conf
# Generated by NetworkManager
search localdomain
nameserver 192.168.2.1
nameserver 8.8.8.8
Anybody any clue?