Unfortunately once a version of Ubuntu becomes unsupported you can run into problems upgrading to the latest version. As is the case when you try to upgrade disco to focal. Ubunut 19.04 to 20.04.
A work around is to update the apt sources and then run an update
Update Apt Sources with.
sudo sed -i 's/disco/focal/g' /etc/apt/sources.list
Now Upgrade with the following two commands.
sudo apt update
sudo apt -y dist-upgrade
More info at the following link.
Install with snap
sudo snap install nextcloud
Set user and password for NextCloud
sudo nextcloud.manual-install nextcloudadmin password
Allow https access for firewall
sudo ufw allow 80,443/tcp
For the following steps to work, you’ll need an A record setup on your domain name server to point a domain to your Next Cloud servers public ip address. Change www.example.com in the following steps to the domain name you’ve setup.
View trusted domains
sudo nextcloud.occ config:system:get trusted_domains
Setup new trusted domain. Change www.example.com with your domain.
sudo nextcloud.occ config:system:set trusted_domains 1 --value=www.example.com
Run through Lets Encrypt to setup a SSL certificate.
sudo nextcloud.enable-https lets-encrypt
Should be able to access NextCloud from a web browser www.example.com
The network configuration settings for the server edition of Ubuntu are now stored in the following location. Create the file if it does not exist.
sudo vi /etc/netplan/01-network-manager-all.yaml
Add or edit the config file to the following. Change eno1 to your interface name and the address and gateway to the appropriate IP’s
For more information, see netplan(5).
network:
version: 2
renderer: networkd
ethernets:
eno1:
dhcp4: no
addresses: [192.168.200.24/24]
gateway: 192.168.200.1
nameservers:
addresses: [8.8.8.8,8.8.4.4]
Now apply the changes with the following command.
sudo netplan apply