How to login to Atlas after kerberizing sandbox cluster?

I have installed the HDP sandbox HDP-3.0.1.0 (3.0.1.0-187) using Docker and Kerberized the cluster. 

I can list the principles from the keytab file like this:

klist -kte /etc/security/keytabs/atlas.service.keytab

 Which gives the following output:

Keytab name: FILE:/etc/security/keytabs/atlas.service.keytab
KVNO Timestamp           Principal
---- ------------------- ------------------------------------------------------
   7 12/04/2019 10:27:18 atlas/sandbox-hdp.hortonworks.com@MYREALM.TLD (des-cbc-md5)
   7 12/04/2019 10:27:18 atlas/sandbox-hdp.hortonworks.com@MYREALM.TLD (des3-cbc-sha1)
   7 12/04/2019 10:27:18 atlas/sandbox-hdp.hortonworks.com@MYREALM.TLD (arcfour-hmac)
   7 12/04/2019 10:27:18 atlas/sandbox-hdp.hortonworks.com@MYREALM.TLD (aes256-cts-hmac-sha1-96)
   7 12/04/2019 10:27:18 atlas/sandbox-hdp.hortonworks.com@MYREALM.TLD (aes128-cts-hmac-sha1-96)

Please forgive my stupidity, but how can I now login to Atlas UI?

I've tried the following "usernames" all without avail:

- atlas

- atlas/sandbox-hdp.hortonworks.com

- atlas/sandbox-hdp.hortonworks.com/MYREALM.TLD (i can get a valid ticket using kinit using this one)

- admin

- raj_ops (i can login to Ambari with this one)

p.s. I've used several password combinations like "admin", "raj_ops", "bigdata", "[mykerberospass]"...