DB version: 19C
OS : Oracle Linux 7.6
I am trying to install 19c Oracle Database software.
I unzipped the 19c installation files to ORACLE_HOME. And then I invoked runInstaller script.
For 15 minutes, it was showing the following blank screen

After 15 minutes, the following became visible.

Then I clicked next for the next few screens and reached prerequisites screen. And, again , it was stuck for another 20 minutes with the following screen but managed to get past it and finish the installation.

Any idea what could be root cause of the first blank screen and the super slowness at prerequisite screen ?
I have installed oracle-database-preInstall-19c package. .