How to set /etc/apt/apt.conf on a Linux subsystem for windows when Windows has automatically proxy setup checked?

On my Windows machine, proxy settings are basic:

Automatic Proxy setup: Automatically detect settings : checked

On my Windows machine, I've installed a Linux subsystem (Ubuntu). I'm trying to perform a sudo apt update or a sudo apt install .... Apparently, in order to get this done, I need to fill in /etc/apt/apt.conf (this file does not exist yet).

I've created that file and very naïvely, I've entered the following:

Linux Prompt> cat apt.conf
Acquire::http::proxy "";
Acquire::https::proxy "";
Acquire::ftp::proxy "ftp://<proxy>";
Acquire::socks::proxy "socks:<proxy>";

This, obviously, does not work, and I don't know about any basic proxies, used by my computer, so this leaves me with two possibilities:

• Either I search for a proxy, used by my computer, and I fill it in in /etc/apt/apt.conf file.
• Either I configure /etc/apt/apt.conf in order to detect proxy settings automatically, just like the "parent" Windows machine.

Which of the two options is best and how do I do it?

Thanks

Edit, some background

I wanted to do some sudo apt install (it's a consequence of this Superuser question, but as an example, let's take "emacs-gtk"):

Linux Prompt> sudo apt install emacs-gtk
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package emacs-gtk

When I do a sudo apt update:

Get:1 focal InRelease
Err:1 focal InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:2 focal-security InRelease
Err:2 focal-security InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:3 focal-updates InRelease
Err:3 focal-updates InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:4 focal-backports InRelease
Err:4 focal-backports InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Reading package lists... Done
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository ' focal InRelease' is not signed.
E: Failed to fetch Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository ' focal-security InRelease' is not signed.
E: Failed to fetch Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository ' focal-updates InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository ' focal-backports InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

As requested: I pinged "8.8.8.8", and there everything seems to be fine:

Linux Prompt> ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=116 time=9.47 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=116 time=9.84 ms
...
^C
--- 8.8.8.8 ping statistics ---
6 packets transmitted, 6 received, 0% packet loss, time 5007ms
rtt min/avg/max/mdev = 9.164/9.388/9.838/0.226 ms

I thought that the apt install problems were due to the /etc/apt/apt.conf file (containing the proxy settings), hence my question.

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