Installing Munin on Ubuntu 20

Useful Links: https://www.howtoforge.com/tutorial/server-monitoring-with-munin-and-monit-on-ubuntu-16-04-lts/
https://www.digitalocean.com/community/tutorials/how-to-install-the-munin-monitoring-tool-on-ubuntu-14-04
Following worked for me without any changes. 

As root or using sudo option, install Munin (of course, do an update 1st) # apt install munin munin-node # systemctl restart munin-node

Alias /munin /var/cache/munin/www
<Directory /var/cache/munin/www>
 # Require local
 Require all granted
 Options FollowSymLinks SymLinksIfOwnerMatch
 Options None
</Directory>

ScriptAlias /munin-cgi/munin-cgi-graph /usr/lib/munin/cgi/munin-cgi-graph
<Location /munin-cgi/munin-cgi-graph>
 # Require local
 Require all granted
 Options FollowSymLinks SymLinksIfOwnerMatch
 <IfModule mod_fcgid.c>
 SetHandler fcgid-script
 </IfModule>
 <IfModule !mod_fcgid.c>
 SetHandler cgi-script
 </IfModule>
</Location> 

Appendix

root@linux-u20:~# apt install munin munin-node Reading package lists... Done Building dependency tree Reading state information... Done Suggested packages: munin-plugins-java The following NEW packages will be installed munin munin-node 0 to upgrade, 2 to newly install, 0 to remove and 0 not to upgrade. Need to get 71.8 kB/204 kB of archives. After this operation, 919 kB of additional disk space will be used. Get:1 http://gb.archive.ubuntu.com/ubuntu focal/universe amd64 munin-node all 2.0.56-1ubuntu1 [71.8 kB] Fetched 71.8 kB in 0s (843 kB/s) Preconfiguring packages ... Selecting previously unselected package munin. (Reading database ... 175120 files and directories currently installed.) Preparing to unpack .../munin_2.0.56-1ubuntu1_all.deb ... Unpacking munin (2.0.56-1ubuntu1) ... Selecting previously unselected package munin-node. Preparing to unpack .../munin-node_2.0.56-1ubuntu1_all.deb ... Unpacking munin-node (2.0.56-1ubuntu1) ... Setting up munin (2.0.56-1ubuntu1) ... apache2_invoke: Enable configuration munin.conf Setting up munin-node (2.0.56-1ubuntu1) ... Initializing plugins..done. Restarting munin-node..Created symlink /etc/systemd/system/multi-user.target.wants/munin-node.service → /lib/systemd/system/munin-node.service. Processing triggers for man-db (2.9.1-1) ... Processing triggers for systemd (245.4-4ubuntu3.3) ...