I have what may be a unique situation.
I live in a small village and have two choices of internet provider, neither of which provide IPV6.
In order to have IPV6 I use a reputable tunnel broker that provides IPV6 to my network.
It is the only way for me to use it and when it works it is faster and just better than IPV4.
But there are some sites and companies that just do full VPN blocks even though mine is a registered non-anonymous VPN.
On all of my machines where it has become an issue I have been able to change the machine preferences normally in Linux I can edit the /etc/gai.conf to prefer IPV4.
How can I do this on HAOS, I want to be able to keep IPV6 more and more services(matter) are requiring or preferring it but until I can have full IPV6 with a local provider I am stuck in this middle ground.
Debian supports editing /etc/gai.conf but I obviusly don’t have access to that level of detail.
Right now I cannot update Matter Server, supervisor logs give me a timeout for and just today Nabu Casa decided that I was off-line for what I suspect is the same reason.
Logger: homeassistant.components.websocket_api.http.connection
Source: components/websocket_api/commands.py:331
integration: Home Assistant WebSocket API (documentation, issues)
First occurred: 8:17:44 PM (3 occurrences)
Last logged: 8:48:21 PM
[140446774830208] Error during service call to update.install: Error updating Matter Server: An unknown error occurred with addon core_matter_server. Check supervisor logs for details (check with 'ha supervisor logs')
[140446728641952] Error during service call to update.install: Error updating Matter Server: An unknown error occurred with addon core_matter_server. Check supervisor logs for details (check with 'ha supervisor logs')
[140446774834208] Error during service call to update.install: Error updating Matter Server: An unknown error occurred with addon core_matter_server. Check supervisor logs for details (check with 'ha supervisor logs')

You need IPV6 on you home network, not an ipv6 connection to the internet…
If you are using the ISP’s router put your own router in front of that and run IPV6 on your home network.
Simply connect your own router’s WAN to the ISP’s network port, then set your router up any way you like. I have 2 set-ups like this.