How to Uploading Files to Folder Outside of Web Console?

I’m running Nextcloud 20 inside of a Docker container on a local server to replace one that I have been running in a DigitalOcean droplet.

Nextcloud version : 20
Operating system and version: Debian GNU/Linux 10
Apache or nginx version: Unsure. apt list doesn’t not show nginx installed. There is a docker container using image “jwilder/nginx-proxy:alpine”. It doesn’t show the version.
PHP version: v7.4.13

However, I’m having problems getting Nextcloud to “see” the files in the folder I created and uploaded files to from the DO droplet.

Steps to replicate

  1. Use docker cp to copy the files in the DO container into the local filesystem.
  2. Tar / Gzip the files into an archive file.
  3. Upload then extract the archive onto the docker host filesystem.
  4. Use docker cp again to copy the files from the host filesystem to the docker container filesystem ( destination /var/www/html/data/admin/files/joplin ) .
  5. chmod 755 joplin folder.
  6. chown -R www-data:www-data joplin to change the user/group for the files. They were 1000:1000 before that.
  7. runuser -u www-data -- php /var/www/html/occ files:scan --all to index the new file. The output of the command shows the correct count.

However, I cannot view the files in the folder while logged in as the admin user. When I click on the folder, the browser window sits there for about 1 minute before kicking me back to the parent director.
The notification “this directory is unavailable” displays in the browser.

Log output - these errors repeated plus some webdav errors from my webdav clients. I can add those if needed. But my main concern is seeing the contents of the Joplin directory.

Error: Cannot modify header information - headers already sent by (output started at /var/www/html/3rdparty/sabre/http/lib/Sapi.php:132) at /var/www/html/apps/dav/lib/Connector/Sabre/File.php#691
Error: file_put_contents(/var/www/html/data/admin/files/joplin/locks/sync_desktop_c709f2fd7ab34c5db0bc4cbdf398e89a.json.ocTransferId212732564.part): failed to open stream: Permission denied at /var/www/html/lib/private/Files/Storage/Local.php#559

config.php contents ( passwords and other secrets removed )

root@3fe896e27d04:/var/www/html# cat config/config.php 
$CONFIG = array (
  'htaccess.RewriteBase' => '/',
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'apps_paths' => 
  array (
    0 => 
    array (
      'path' => '/var/www/html/apps',
      'url' => '/apps',
      'writable' => false,
    1 => 
    array (
      'path' => '/var/www/html/custom_apps',
      'url' => '/custom_apps',
      'writable' => true,
  'instanceid' => 'oc7ezugqzso5',
  'passwordsalt' => '',
  'secret' => '',
  'trusted_domains' => 
  array (
    0 => '',
  'datadirectory' => '/var/www/html/data',
  'dbtype' => 'mysql',
  'version' => '',
  'overwrite.cli.url' => '',
  'dbname' => 'nextcloud',
  'dbhost' => 'db:3306',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => 'nextclouddb',
  'dbpassword' => '',
  'installed' => true,