Have not been able yet to make a test-install on physical server for Ubuntu.
But did an install on CentOS which did behave normally, the first 2 times at least. Again as a XenServer VM.
I did this install 3 times, and I noticed that the install wizard error seems to come from the screen where I am meant to select the backend (LDAP, MySQL etc).
This screen behaves very awkwardly under CentOS and also under Ubuntu. One cannot move the cursor.
I find no way to select the NEXT button.
The only way I found was pressing Alt+N, then it goes further, but in that case it seems to go two screens further (skipping the LDAP domain and MySQL password entry), seemingly this indicates LDAP is NOT selected.
Also when this happens, then every time I do NOT get the optional components screen.
In CentOS, I cannot change the backend options. If I press the space bar, it sometimes manages to jump to PostgreSQL. Next few presses does not change anything. I cannot select the NEXT. I then use Alt-N again as above, but then I get the SAME ERROR as I had in Ubuntu - does not ask for LDAP domain or MySQL password and the optional-components screen is missing, and it gives this error message upon completion as noted above (cannot find optional_components).
The only way I found was to just don't even try to select anything but press ENTER. Then it works and then it also does show the optional_components screen and completes correctly.
Looks like my above-mentioned bug is related to this screen of the installer.