Login to ubuntu 21.04 sever.
Run the following commmand to download nextcloud.
sudo snap install nextcloud
root@vps:~# sudo snap install nextcloud nextcloud 18.0.4snap1 from Nextcloud✓ installed
Now type your IP address in the URL to launch the nextcloud.
You will have to create admin account for ownCloud
Enter the username and password which you want to set.