Installing Duplicati 2.6 on CentOS 8

install_duplicati_centos8.sh

# Start this script while logged in as root.	

# Preparations:	
# Update manually with yum if it's a new OS installation.
	# yum update -y && reboot
	yum install wget curl -y
	
	mkdir /downloads
	cd /downloads
	
# Install mono as per the instructions on: https://www.mono-project.com/download/stable/#download-lin-centos	
#  at the time of this writing (2021-05-11) it was as so:	
	rpmkeys --import "http://pool.sks-keyservers.net/pks/lookup?op=get&search=0x3fa7e0328081bff6a14da29aa6a19b38d3d831ef"
	curl https://download.mono-project.com/repo/centos8-stable.repo | tee /etc/yum.repos.d/mono-centos8-stable.repo
	yum install mono-devel -y

# Install additional requirements:	
	yum install sqlite gtk-sharp2 -y
	
# Download the latest Duplicati for CentOS. Get the URL from: https://www.duplicati.com/download	
# e.g.:	
	wget https://updates.duplicati.com/beta/duplicati-2.0.6.1-2.0.6.1_beta_20210503.noarch.rpm
	
# Install as per the instructions at https://duplicati.readthedocs.io/en/latest/02-installation/ (at the bottom of the page)	
# Note that yum install does not work. Use something like:	
	rpm -ivh --nodeps duplicati-2.0.6.1-2.0.6.1_beta_20210503.noarch.rpm
# Ignore the error about a service not existing.	

# Create Duplicati service options file:	
	echo "# Defaults for duplicati initscript" > /etc/default/duplicati
	echo "# sourced by /etc/init.d/duplicati" >> /etc/default/duplicati
	echo "# installed at /etc/default/duplicati by the maintainer scripts" >> /etc/default/duplicati
	echo "" >> /etc/default/duplicati
	echo "#" >> /etc/default/duplicati
	echo "# This is a POSIX shell fragment" >> /etc/default/duplicati
	echo "#" >> /etc/default/duplicati
	echo "" >> /etc/default/duplicati
	echo "# Additional options that are passed to the Daemon." >> /etc/default/duplicati
	echo "DAEMON_OPTS=\"--webservice-interface=any --webservice-port=8200 --portable-mode\"" >> /etc/default/duplicati
	
# Create the service:	
	echo "[Unit]" > /etc/systemd/system/duplicati.service
	echo "Description=Duplicati web-server" >> /etc/systemd/system/duplicati.service
	echo "After=network.target" >> /etc/systemd/system/duplicati.service
	echo "" >> /etc/systemd/system/duplicati.service
	echo "[Service]" >> /etc/systemd/system/duplicati.service
	echo "Nice=19" >> /etc/systemd/system/duplicati.service
	echo "IOSchedulingClass=idle" >> /etc/systemd/system/duplicati.service
	echo "EnvironmentFile=-/etc/default/duplicati" >> /etc/systemd/system/duplicati.service
	echo "ExecStart=/usr/bin/duplicati-server \$DAEMON_OPTS" >> /etc/systemd/system/duplicati.service
	echo "Restart=always" >> /etc/systemd/system/duplicati.service
	echo "" >> /etc/systemd/system/duplicati.service
	echo "[Install]" >> /etc/systemd/system/duplicati.service
	echo "WantedBy=multi-user.target" >> /etc/systemd/system/duplicati.service
	
	systemctl enable duplicati.service
	sleep 1
	systemctl daemon-reload
	sleep 1
	
# Start the service:	
	service duplicati start
	sleep 4
	service duplicati status
	
# It's ready.	
# Access the web interface using the favorite browser at http://ip:8200/ or as set in the config file.	

Very helpful script - thank you very much for sharing!
I updated the download links to the newest version before I used it:
https://updates.duplicati.com/beta/duplicati-2.0.6.3-2.0.6.3_beta_20210617.noarch.rpm

Glad I could be of help.

Oh wow, I was so much a Linux n00b back then lol