As of late i have this problem where pages come up blank in Opera mini and mini beta on my old Huawei P6 (i know, i should retire it, but Opera is still pushing updates to it so...).
Weird thing is that they draw fine when i hit the tab switcher button.
I do believe the GPU on the Huawei soc may be a bit wonky, as i have observed oddities with video players in the past. So if Opera has switched to using GPU for drawing it may be a source of problems.