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Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 18.0.2): 19.0.0.12
Operating system and version (eg, Ubuntu 20.04): ubunru 20.04
Apache or nginx version (eg, Apache 2.4.25): nginx 1.19
PHP version (eg, 7.1): 7.4
The issue you are facing:
Good evening, I have version 19 installed, I created users, placed them in groups, different users in different groups. User logins are written in Latin, and the names displayed in Cyrillic. I included myself as an administrator in all user groups, and forbade them to see each other and change files, through the settings in the nextcloud interface. When I try to share a folder or file for some user, and I write his name in Cyrillic, it doesn’t give me anything, but if I write the user name in Latin, then I find it right away. Is this a bug? or is this how it works? And another question, why other users in the groups of which I am not see me in the list of users in my interface? I just don’t show up. My base on Postgresql 12.3
Thank.
Is this the first time you’ve seen this error? (Y/N):
Steps to replicate it:
The output of your Nextcloud log in Admin > Logging:
PASTE HERE
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
PASTE HERE
The output of your Apache/nginx/system log in /var/log/____:
PASTE HERE