How to block adding new keyboard input sources from login display? I'm interesting is there any way to leave only one input source for login display and block (disable) adding new input sources?

UPD: I want to get only 1 (one, single) language (input source), for example english (ABC) and block a possibility (chance) to choose another one (any other) language (input source). To uncheck checkbox with "Show Input menu in Login window" doesn't help in my case. Does anyone (anybody) know any other method?
System Preferences > Users &amp; Groups > Login Options

Uncheck "Show Input menu in login window"