I just tried to install the beta on my rasp pi 3 b+.
On my dell monitor, it said "cannot display this video mode, optimum resolution 1280*1024 at 60hz".
i don't have the rainbow screen.
If i do it on my video projector, it's working fine. But it's not where i want to use it.
With raspbian, no problem on this monitor....
With xubuntu, no problem ( (Unofficial) Xubuntu-core armhf - https://1drv.ms/u/s!AvHY_kl4hMB4gQIR4CLRKQzh-GP0
Can you help, do you know this problem?
maybe something to improve on the next beta....
Thanks anyway, the little i tried, looks good...