I tried your method installing nextcloud on my Odroid HC1 (XU4) and I always get the "Error: Could not download app calendar".
I tried removing the containers , removing the config files deleting the Images for several times with the same error. Kindly notify if you know a fix for this.
Code
Initializing empty volume..
Making /usr/local/etc/ncp-config.d persistent ...
Making /etc/services-enabled.d persistent ...
Making /etc/letsencrypt persistent ...
Making /etc/shadow persistent ...
Making /etc/cron.d persistent ...
Making /etc/cron.daily persistent ...
Making /etc/cron.hourly persistent ...
Making /etc/cron.weekly persistent ...
Making /usr/local/bin persistent ...
Making /etc/apache2 persistent ...
Starting PHP-fpm
Starting Apache
Starting mariaDB
2020-06-23 8:27:07 0 [Note] mysqld (mysqld 10.3.22-MariaDB-0+deb10u1) starting as process 201 ...
Starting Redis
Starting Cron
Starting Postfix
Uninitialized instance, running nc-init...
Running nc-init
Setting up a clean Nextcloud instance... wait until message 'NC init done'
Setting up database...
Setting up Nextcloud...
Nextcloud was successfully installed
Set mode for background jobs to 'cron'
System config value tempdirectory set to string /var/www/nextcloud/data/tmp
System config value mysql.utf8mb4 set to boolean true
System config value trusted_domains => 11 set to string <MY IP>
System config value trusted_domains => 1 set to string 172.17.0.4
System config value trusted_domains => 5 set to string nextcloudpi.local
System config value trusted_domains => 7 set to string nextcloudpi
System config value trusted_domains => 8 set to string nextcloudpi.lan
System config value mail_smtpmode set to string sendmail
System config value mail_smtpauthtype set to string LOGIN
System config value mail_from_address set to string admin
System config value mail_domain set to string ownyourbits.com
nextcloudpi enabled
Error: Could not download app calendar
Init done