New installer does not copy proxy settings from live system to the installed system

[Norbert]

Steps to reproduce:
1. Download latest ISO, for example -
Ubuntu-MATE 24.04 LTS "Noble Numbat" - Beta amd64 (20240416)
2. Boot the ISO
3. Wait for new installer window to appear, select language, configure a11y, keyboard and network connection, click on "Try Ubuntu MATE"
4. Launch "Network Proxy" (mate-network-properties), set HTTP proxy http://1.2.3.4:3128 in it, hit Close
5. Launch installer again, wait it to finish

Expected result:
* the installed system uses http://1.2.3.4:3128 for APT

Actual result:
* the installed system does not include any mentions of http://1.2.3.4:3128 proxy.

Background: previous traditional Ubiquity installer was able to copy proxy settings into the apt configuration - it wrote
Acquire::http::Proxy "http://1.2.3.4:3128";
into /etc/apt/apt.conf .
But with new modern glossy installer this feature is missed.
It is a big discrepancy for users with configured Squid Deb Proxyies in their networks.

[Norbert (nrbrtx)]

Info from live system:
```
$ snap list
Name Version Rev Tracking Publisher Notes
bare 1.0 5 latest/stable canonical** base
core22 20240111 1122 latest/stable canonical** base
firefox 124.0.2-1 4090 latest/stable/… mozilla** -
firmware-updater 0+git.5007558 127 latest/stable/… canonical** -
gnome-42-2204 0+git.510a601 176 latest/stable/… canonical** -
gtk-common-themes 0.1-81-g442e511 1535 latest/stable/… canonical** -
snap-store 0+git.1419621 1124 latest/stable/… canonical** -
snapd 2.61.2 21184 latest/stable canonical** snapd
snapd-desktop-integration 0.9 157 latest/stable/… canonical** -
subiquity 22.02.2+git2159.2550aaa7 5722 latest/stable/… canonical** classic
ubuntu-desktop-bootstrap 0+git.4fb1e2ee 113 latest/stable/… canonical** classic

$ gsettings list-recursively | grep -E "proxy.http host|proxy.http port"
org.gnome.system.proxy.http host '1.2.3.4'
org.gnome.system.proxy.http port 8000
```

[Norbert (nrbrtx)]

Proxy settings are not copied using
Ubuntu-MATE 24.04 LTS "Noble Numbat" - Beta amd64 (20240419)
with
ubuntu-desktop-provision 158.

[Sebastien Bacher (seb128)]

Using the current image do you get the gsettings keys copied and not the apt config from the initial description? or are the gsettings configuration also missing?

[Norbert (nrbrtx)]

Yes, via gsettings by running "Network Proxy" (mate-network-properties) while installer window is closed.
Please download UM 20.04 LTS and check the expected traditional behavior by yourself.