Cannot modify self's group (and other properties)

Nextcloud version (eg, 12.0.2): 18.0.3
Operating system and version (eg, Ubuntu 17.04): Ubuntu 18.04
Apache or nginx version (eg, Apache 2.4.25): nginx/1.10.3
PHP version (eg, 7.1): PHP 7.3.16

The issue you are facing:
User is not able to add itself to groups.

Is this the first time you’ve seen this error? (Y/N): Y

Steps to replicate it:

  1. Log into NC as admin
  2. Click on the user icon and choose User (url settings/users)
  3. Try to edit yourself, like for adding to a group: it’s impossible

In order to add yourself to a group you must ask another admin to do the task