Install fails on Ubuntu 20

I ran the installer for the deb file like this:

sudo apt install ./rustdesk-1.1.9.deb

and saw this outcome.

Setting up python3-setuptools (59.6.0-1.2) ...
Setting up python3-wheel (0.37.1-2) ...
Setting up python3-pip (22.0.2+dfsg-1) ...
Setting up libgcc-11-dev:amd64 (11.2.0-19ubuntu1) ...
Setting up libc6-dev:amd64 (2.35-0ubuntu3.1) ...
Setting up binutils-x86-64-linux-gnu (2.38-3ubuntu1) ...
Setting up rustdesk (1.1.9) ...
WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7f977d6d8430>: Failed to establish a new connection: [Errno 101] Network is unreachable')': /simple/pynput/
WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7f977d6d8640>: Failed to establish a new connection: [Errno 101] Network is unreachable')': /simple/pynput/
WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7f977d6d8850>: Failed to establish a new connection: [Errno 101] Network is unreachable')': /simple/pynput/
WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7f977d6d8af0>: Failed to establish a new connection: [Errno 101] Network is unreachable')': /simple/pynput/

I believe it is likely due to network proxy. The proxy is given to apt in /etc/apt/apt.conf but looks like pip does not inherit that.

Start by reproducing sudo apt install ./rustdesk-1.1.9.deb on Ubuntu 20 with the proxy configured in /etc/apt/apt.conf, then inspect the installer’s pip step and its attempt to fetch pynput. Done means the deb installation can obtain its Python dependency through the configured proxy instead of failing with a network-unreachable error.