html5_url is a column in the kaltura.ui_conf table.
As for the files, the one owned by root has r permissions for other, so Studio should still be able to read it but best to set all flles under /opt/kaltura/web//content/generatedUiConf to be writeable to the Apache user.
Also, when I wrote $PLAYER_ID, I meant for you to replace it with your actual UI conf ID for the player, you can see that in the Studio's index page.