Are you absolutely sure you had one monitor plugged into the mobo jack? (multi-head).
Multi-head with X server is very hard to get the setup right..

It is much easier to use the desktop if both monitors are plugged into the same GPU..
Unless you have a top-end intel CPU with HD5300/iris-pro/iris 530, the lowly GT610 is probably faster.

The onboard graphics is intel; the FOSS driver is included with ubuntu. Usually the support get better.

IIUC Multi-head in the past required to have a custom xorg.conf file that specifies loading driver for each GPU.
And you had to use xinerama to join the mutli-head monitors into one unified display.