This article assumes that you have all of your files in the /volume1 folder. In order to be able to access these files from within Nextcloud’s External Storage app, you will need to add the following line in /etc/fstab:

/volume1 /mnt/volume1 none bind

Also, until Redis packages are made to take advantage of the larger page size of the Raspberry Pi 5, we will have to add the following line to /boot/firmware/config.txt:

kernel=kernel8.img

Now install nextcloud using the following commands:

$ sudo apt install snapd
$ sudo snap install snapd
$ sudo snap install nextcloud

You should now be able to access the Nextcloud installer by entering the Pi’s IP address in a browser on the same network. If you want to install an SSL certificate then use the following command:

$ sudo /snap/bin/nextcloud.enable-https lets-encrypt

You will be asked to provide an email address and the domain name to be used. You will need to add the following lines to the config.php file for Nextcloud. This file should be located in /var/snap/nextcloud/current/nextcloud/config/config.php.

'overwritehost' => 'example.com',
'overwriteprotocol' => 'https',
'trusted_domains' => 
array (
  0 => 'example.com',
),

Now you should be able to access Nextcloud using your domain name.

References

https://help.nextcloud.com/t/redis-crashing-on-startup-after-swapping-rpi4-8gb-with-rpi5-8gb/182242

https://snapcraft.io/install/nextcloud/debian

https://github.com/nextcloud-snap/nextcloud-snap/wiki/Nextcloud-snap-step-by-step/38e0ac1ceb23a990f10471546b95e2f04f060314