Install OpenResty on Ubuntu from source code.

install_openresty.sh

#!/bin/bash
set -e
rm -rf openresty-1.19.3.2 openresty-1.19.3.2.tar.gz

apt-get update -y
apt-get install -y libpcre3-dev \
  libssl-dev \
  perl \
  make \
  build-essential \
  curl \
  zlib1g-dev

curl -LO https://openresty.org/download/openresty-1.19.3.2.tar.gz
tar zxf openresty-1.19.3.2.tar.gz
cd openresty-1.19.3.2

./configure \
  --with-http_gzip_static_module \
  --with-http_v2_module \
  --with-http_stub_status_module

make
make install

mkdir -p /usr/lib/systemd/system
cat > /tmp/openresty.service <<EOF
# Stop dance for OpenResty
# =========================
#
# ExecStop sends SIGSTOP (graceful stop) to OpenResty's nginx process.
# If, after 5s (--retry QUIT/5) nginx is still running, systemd takes control
# and sends SIGTERM (fast shutdown) to the main process.
# After another 5s (TimeoutStopSec=5), and if nginx is alive, systemd sends
# SIGKILL to all the remaining processes in the process group (KillMode=mixed).
#
# nginx signals reference doc:
# http://nginx.org/en/docs/control.html
#
[Unit]
Description=The OpenResty Application Platform
After=syslog.target network-online.target remote-fs.target nss-lookup.target
Wants=network-online.target
[Service]
Type=forking
PIDFile=/usr/local/openresty/nginx/logs/nginx.pid
ExecStartPre=/usr/local/openresty/nginx/sbin/nginx -t -q -g 'daemon on; master_process on;'
ExecStart=/usr/local/openresty/nginx/sbin/nginx -g 'daemon on; master_process on;'
ExecReload=/usr/local/openresty/nginx/sbin/nginx -g 'daemon on; master_process on;' -s reload
ExecStop=-/sbin/start-stop-daemon --quiet --stop --retry QUIT/5 --pidfile /usr/local/openresty/nginx/logs/nginx.pid
TimeoutStopSec=5
KillMode=mixed
[Install]
WantedBy=multi-user.target
EOF

# systemctl enable openresty
# systemctl start openresty
# systemctl status openresty

rm -rf openresty-1.19.3.2 openresty-1.19.3.2.tar.gz