Nextcloud iOS app stuck in "classic" login - No QR code or "app password" login

Nextcloud version (eg, 20.0.5): 21.0.3
Operating system and version (eg, Ubuntu 20.04): Ubuntu server 18.04
Apache or nginx version (eg, Apache 2.4.25): ??? (don’t know how to check that)
PHP version (eg, 7.4): 7.4.21

On July 9 iOS app prompted me to login, for reasons that are not clear to me but may be related to:

  • Nextcloud 21.0.3 (snap) update on July 9
  • Update of iOS app to 4.0.4 on July 2
  • Restarting my iPhone

Because I had not needed to login for months (since my initial setup), I did not recall that I had used an “app password” generated at
https://[my-cloud-url]/index.php/settings/user/security

So I selected “classic login” on the iOS app. I logged in successfully, but now I cannot get back to a login screen on the iOS app that shows the QR code option.
QR_icon
It seems to be stuck at the “classic login” screen, It does show an “app token” option, but following that link does not show the QR code option either.

Steps to replicate it:

  1. Go to https://[my-cloud-url]/index.php/settings/user/security
  2. Revoke “Nextcloud iOS app Nextcloud”
  3. Open my iOS Nextcloud app; generates error and redirects to login screen
  4. No QR code option at login nor any link to revert to “app password” mode

The output of my Nextcloud log in Admin > Logging (repetitive lines removed):

{"reqId":"MnH...vEH","level":2,"time":"2021-07-10T19:52:43+00:00","remoteAddr":"98.xxx.xxx.xxx","user":"my-username","app":"no app in context","method":"GET","url":"/index.php/settings/user/privacy","message":"Invalid privacyPolicyUrl data provided to provideInitialState by privacy","userAgent":"Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:89.0) Gecko/20100101 Firefox/89.0","version":"21.0.3.1","id":"60e...637"}
...
{"reqId":"c9T...pqc0","level":2,"time":"2021-07-10T19:50:59+00:00","remoteAddr":"98.xx.xxx.xxx","user":"--","app":"core","method":"GET","url":"/index.php/core/preview.png?file=Readme.md&x=1024&y=1024&a=1&mode=cover","message":"Login failed: 'my-username' (Remote IP: '98.xxx.xxx.xxx')","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/4.0.4","version":"21.0.3.1","id":"60e...379"}
...
{"reqId":"aGd...4uL","level":0,"time":"2021-07-09T15:27:42+00:00","remoteAddr":"","user":"--","app":"files_sharing","method":"","url":"--","message":"/appinfo/app.php is deprecated, use \\OCP\\AppFramework\\Bootstrap\\IBootstrap on the application class instead.","userAgent":"--","version":"21.0.1.1","id":"60e...eb0"}
{"reqId":"aGd...4uL","level":0,"time":"2021-07-09T15:27:42+00:00","remoteAddr":"","user":"--","app":"core","method":"","url":"--","message":"starting upgrade from 21.0.1.1 to 21.0.3.1","userAgent":"--","version":"21.0.1.1","id":"60e...f95"}

The output of my config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
Comments removed for brevity.

<?php

$snap_current = getenv('SNAP_CURRENT');
$snap_data_current = getenv('SNAP_DATA_CURRENT');

$CONFIG = array(

'apps_paths' => array(
	
	array(
		'path'=> $snap_current.'/htdocs/apps',
		'url' => '/apps',
		'writable' => false,
	),

	array(
		'path'=> $snap_data_current.'/nextcloud/extra-apps',
		'url' => '/extra-apps',
		'writable' => true,
	),
),

'supportedDatabases' => array(
	'mysql',
),

'memcache.locking' => '\OC\Memcache\Redis',
'memcache.local' => '\OC\Memcache\Redis',
'redis' => array(
    'host' => getenv('REDIS_SOCKET'),
    'port' => 0,
),

'log_type' => 'file',
'logfile' => $snap_data_current.'/logs/nextcloud.log',
'logfilemode' => 0640,
);

The output of your Apache/nginx/system log in /var/log/____:

I cannot find this. Perhaps because it’s buried in snap somewhere?

PASTE HERE

After weeks without a response, I decided to delete and reinstall the Nextcloud iOS app. That fixed my problem, i.e., I was able to authenticate my newly downloaded iOS app with an “app password”/QR code.

I think there may be a small bug in the iOS app because this feature (QR login) disappeared after I opted for “classic login.”