do-release-upgrade ignores APT proxy exemption

When I try to check for an upgrade, this is what happens:

# do-release-upgrade -c
Checking for a new Ubuntu release
Failed to connect to https://changelogs.ubuntu.com/meta-release-lts. Check your Internet connection or proxy settings
There is no development version of an LTS available.
To upgrade to the latest non-LTS develoment release
set Prompt=normal in /etc/update-manager/release-upgrades.

With tcpdump, I discovered that do-release-upgrade tries to connect the configured APT-Cacher-NG proxy. The proxy only listens on plaintext HTTP (TCP:80), while the script tries to connect it on HTTPS (TCP:443), because it wants to download meta-release-lts through an https:// URL. Since I have no intention to configure SSL certificates on the proxy for the sole reason to enable upgraders to operate, I thought I'd rather exempt it from the APT proxy setting.

Currently, I have this APT proxy configuration under /etc/apt/apt.conf.d:

Acquire::http {
 Proxy::changelogs.ubuntu.com "DIRECT";
 Proxy "http://taranis.lan";
};
Acquire::https {
 Proxy::changelogs.ubuntu.com "DIRECT";
};

I added an explicit section for https too, just in case. According to man apt-transport-http, the syntax should be correct and `apt-config dump` reports that it correctly parsed the config file and understands that it needs to exempt changelogs.ubuntu.com.

Acquire::http::Proxy "http://taranis.lan";
Acquire::http::Proxy::changelogs.ubuntu.com "DIRECT";
Acquire::https::Proxy "";
Acquire::https::Proxy::changelogs.ubuntu.com "DIRECT";

However, trying `do-release-upgrade -c` has the same result, the upgrader still wants to get the meta-release file via the proxy. It is a strange situation, because it seems `do-release-upgrade` wants to honour the APT proxy configuration, but it ignores the exemptions. In my case, it would be better to ignore the proxy altogether.

I have this proxy for quite a while and the server was configured to use it, and I don't remember encountering this issue on any previous release upgrade, but I haven't run one since 2018. I guess the feature of honouring the APT proxy config was added recently in the last 2 years. I have this issue on my Bionic server, and I reproduced it on a pristine Focal VM installation as well.

I think the intended or desirable behaviour would be to adhere to the APT proxy configuration in its entirety, including the exemptions.