You can turn off security entirely, which will disable the login screen, by setting
xpack.security.enabled: false in elasticsearch.yml and kibana.yml, but that may not be what need.
Is your goal to have users be automatically logged in with a certain role (say, read only?)?
The latter can be done with a reverse proxy. There is some good info on this here:
As for the anonymous authentication, I'm not sure how kibana is supposed to act when that is set up in elasticsearch, but I'll try to find out more information.