Register not working (worked previously)

Steps to reproduce

try registering a new user using the registration page

Expected behaviour

user should receive an email

Actual behaviour

big red error on the register page

Server configuration

Operating system: ubuntu 22.04

Web server: nginx

Database: mariadb

PHP version: 8.2

Nextcloud version: (see Nextcloud admin page) 28.0.2

Updated from an older Nextcloud/ownCloud or fresh install: updated

Where did you install Nextcloud from: official website

Signing status:

Login as admin user into your Nextcloud and access 
http://example.com/index.php/settings/integrity/failed 
paste the results here.

List of activated apps:

If you have access to your command line run e.g.:
sudo -u www-data php occ app:list
from within your Nextcloud installation folder

The content of config/config.php:

If you have access to your command line run e.g.:
sudo -u www-data php occ config:list system
from within your Nextcloud installation folder

An unhandled exception has been thrown:
OCP\HintException: [0]: Memcache OC\Memcache\APCu not available for local cache (Is the matching PHP module installed and enabled?)

or 

Insert your config.php content here
(Without the database password, passwordsalt and secret)

Are you using external storage, if yes which one: local/smb/sftp/... no

Are you using encryption: yes/no no (not sure)

Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/... no

With access to your command line run e.g.:
sudo -u www-data php occ ldap:show-config
from within your Nextcloud installation folder

same as previous commands

Without access to your command line download the data/owncloud.db to your local
computer or access your SQL server remotely and run the select query:
SELECT * FROM `oc_appconfig` WHERE `appid` = 'user_ldap';


Eventually replace sensitive data as the name/IP-address of your LDAP server or groups.

Client configuration

Browser: Brave

Operating system: Windows 11

Logs

Web server error log

Insert your webserver log here no errors in my webserver log

Nextcloud log (data/nextcloud.log)

Insert your Nextcloud log here

Browser log

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log
c) ...

Start by reproducing registration on the reported Nextcloud 28.0.2 setup and inspect the provided configuration and logs, including the APCu exception and SMTP settings. The report names no source files or tests; done means identifying the cause of the registration-page error and confirming that a new user receives the expected email.