3D accelaration not supported on Mac host with Ubuntu guest with new 5.26

[AALLeeXX]

Hello,

I just installed newly released 5.2.6 on HighSierra macOS 10.13.3 (17D29a) and try booting my Linux Ubuntu, but the display becomes unstable and becomes black before end of boot. Ubuntu never appears. I just shutdown (ACPI shutdown) the machine from the VB windows.
The VB window size for the guest takes different sizes successively, in a loop, 600x800 and another size bigger, while the contents keeps black. This does not stop at all even after several minutes far more that needed to boot Ubuntu.
If I disable the 3D acceleration, it happens Ubuntu boots properly - but of course is pretty slow and hardly usable.

I installed the GuestAdditions and extensions as suggested by VB...
Here the logs I took.

Thanks for any help here ...

[mpack]

Duplicate.

[socratis]

Known issue, reported all over the forums, as mpack said. Try the new 5.2.7 GAs, build 120326 or greater. From the Downloads page, look at the "Important" section closely.