Install i3-gaps on ubuntu 20.04

i3-gaps.sh

#!/bin/bash
sudo apt install -y libxcb1-dev libxcb-keysyms1-dev libpango1.0-dev libxcb-util0-dev libxcb-icccm4-dev libyajl-dev libstartup-notification0-dev libxcb-randr0-dev libev-dev libxcb-cursor-dev libxcb-xinerama0-dev libxcb-xkb-dev libxkbcommon-dev libxkbcommon-x11-dev autoconf libxcb-xrm0 libxcb-xrm-dev automake libxcb-shape0-dev libxcb-xrm-dev

cd /tmp

# clone the repository
git clone https://www.github.com/Airblader/i3 i3-gaps
cd i3-gaps

# compile & install
autoreconf --force --install
rm -rf build/
mkdir -p build && cd build/

# Disabling sanitizers is important for release versions!
# The prefix and sysconfdir are, obviously, dependent on the distribution.
../configure --prefix=/usr/local --sysconfdir=/etc --disable-sanitizers
make -j2
sudo make install

setup.md

Setting up i3 / variants

For i3-gaps-rounded

Use git clone https://github.com/resloved/i3.git

If no i3 option in lock screen

Paste the following into /usr/share/xsessions/i3.desktop

[Desktop Entry]
Name=i3
Comment=improved dynamic tiling window manager
Exec=i3
TryExec=i3
Type=Application
X-LightDM-DesktopName=i3
DesktopNames=i3
Keywords=tiling;wm;windowmanager;window;manager;

Replaced line:
deb https://ppa.launchpadcontent.net/regolith-linux/release/ubuntu/ impish main

Works for me