I flashed Ubuntu MATE 18.04 onto my microSDHC card and booted my Raspberry Pi 3 B with it.
Unfortunately I do net get any output on my monitor which is connected via a HDMI cable.
The SD card is working fine and the Raspberry Pi seems to boot, as it got assigned a network IP address.
I tried to boot with my old Ubuntu MATE 16.04 and there I have a output on my monitor.
What can I do to fix this problem? Is this a bug in Ubuntu MATE 18.04?