SHELL

depends: libssl1.1 (>= 1.1.1) but it is not installable

# I see two options:

# 1. Try to install libssl manually (the exact version from official repository):

sudo apt install libssl1.1=1.1.0g-2ubuntu4.3
# 2. Remove ppa:ondrej/php from the system:

sudo apt install ppa-purge
sudo ppa-purge ppa:ondrej/php
# and then install lighttpd

sudo apt install lighttpd