Ubuntu 18.04 install steps:
$ sudo apt update
$ sudo apt upgrade
$ sudo apt install software-properties-common
$ sudo apt install python-pip -y
$ sudo apt install python3-pip -y
$ sudo apt install python3.7-venv -y
$ sudo apt install python3.7-dev -y
Then follow instructions from https://github.com/willcl-ark/lightning/blob/lnproxy/doc/INSTALL.md :
$ git clone https://github.com/willcl-ark/lightning.git lightning
$ cd lightning
$ git checkout lnproxy
$ python3.7 -m venv .venv
$ source .venv/bin/activate
(.venv) $ pip install --upgrade pip
(.venv) $ pip install lnproxy
(.venv) $ pip install -r requirements.txt
(.venv) $ pip install -r plugins/sauron/requirements.txt
(.venv) $ ./configure --enable-developer && make
(.venv) $ source ./contrib/startup_testnet1.sh
(.venv) $ start_ln
(.venv) $ l1-cli newaddr
.
.
.
When done, deactivate the virtual environment:
(.venv) $ deactivate