I am getting this same problem (black screen that seems to be running but nothing except a black screen is displayed....which occasionally ends up causing the tab to crash...or even Vivaldi in whole). In case it helps, here is an URL that repeatedly causes the black screen and crash:
https://www.denverpost.com/2018/12/16/full-strength-beer-colorado-grocery-stores-new-years-day/
Display/Video hardware info:
Name AMD Radeon HD 8700M Series
PNP Device ID PCI\VEN_1002&DEV_6600&SUBSYS_C0E6144D&REV_00\4&383E238C&0&0008
Adapter Type AMD Radeon Graphics Processor (0x6600), Advanced Micro Devices, Inc. compatible
Adapter Description AMD Radeon HD 8700M Series
Adapter RAM 1.00 GB (1,073,741,824 bytes)
Installed Drivers aticfx64.dll,aticfx64.dll,aticfx64.dll,amdxc64.dll
Driver Version 15.200.1065.0
INF File oem90.inf (ati2mtag_R502 section)
Color Planes Not Available
Color Table Entries Not Available
Resolution Not Available
Bits/Pixel Not Available
Memory Address 0xE0000000-0xEFFFFFFF
Memory Address 0xF7DC0000-0xF7DFFFFF
I/O Port 0x0000EF00-0x0000EFFF
IRQ Channel IRQ 4294967288
Driver c:\windows\system32\drivers\atikmpag.sys (8.14.1.6463, 649.50 KB (665,088 bytes), 2017-10-07 10:03 AM)
Name Intel(R) HD Graphics 4000
PNP Device ID PCI\VEN_8086&DEV_0166&SUBSYS_C0E6144D&REV_09\3&11583659&0&10
Adapter Type Intel(R) HD Graphics Family, Intel Corporation compatible
Adapter Description Intel(R) HD Graphics 4000
Adapter RAM (2,080,374,784) bytes
Installed Drivers igdumdim64.dll,igd10iumd64.dll,igd10iumd64.dll
Driver Version 10.18.10.4653
INF File oem68.inf (iIVBM_w10 section)
Color Planes Not Available
Color Table Entries 4294967296
Resolution 1680 x 1050 x 59 hertz
Bits/Pixel 32
Memory Address 0xF7800000-0xF7BFFFFF
Memory Address 0xD0000000-0xDFFFFFFF
I/O Port 0x0000F000-0x0000F03F
IRQ Channel IRQ 4294967290
Driver c:\windows\system32\drivers\igdkmd64.sys (10.18.10.4653, 3.64 MB (3,811,816 bytes), 2017-05-18 3:11 PM)