[xubuntu] 16.04: No video on AMD A10-6700 (Richland), needs "nomodeset" to boot

Hello there,

today I installed a fresh Xubuntu 16.04 onto my main desktop machine, which uses an AMD A10-6700 ("Richland") processor on a MSI A88XM-E45 Mainboard (a setup well-supported on 14.04). However, when starting the fresh 16.04 install, the keel apparently fails to properly set up the inteal Radeon graphics and triggers a reboot mere seconds after start, which leads me to the Grub menu. The recovery mode works, as does the normal startup procedure if I add "nomodeset" as keel parameter (which the recovery mode also uses, of course). This means I have no 3D acceleration whatsoever.

I couldn't find a bug report quite matching what I'm seeing there - did anybody encounter something similar? Given that I have no screen output when this failure triggers: What log files could contain proper information (provided the keel even gets so far as to properly mount the filesystem)?

Maik