Which version of Ubuntu are you using (series & flavor)? Can you run snap version?
Also; how many tabs do you have open?
Edit: now that I took a second look at it; it seems like you have Ubuntu Software both as a deb and as a snap installed. The snap is the one with a black screen. The snap store on my system only has one row of recommended apps. I think the deb had two rows.
The black screen definitely looks like a bug, though.
I’m on 20.04 LTS. I installed it in February so it had gnome-software at that time by default. Then I also installed snap-store manually at some point before the archive store transition.
Most of those tabs are inactive. Vivaldi loads only those that you open. Atleast if you have the “delayed loading of tabs” enabled (don’t know if that’s default). And you don’t even see all of them in that screenshot because some are grouped.
The black snap-store isn’t a permanent problem. It happens in some sessions. I’m sure if I would restart now and open it in that new session it would be looking as expected.
So I rebooted and snap-store launched with proper theming (Numix Daily theme).
I wonder what goes wrong in those instances where it appears black. Also I’ve seen people posting sreenshots that had it completly transparent or parts of it.
Any theme that’s included in gtk-common-themes should work fine. We will soon have a mechanism to auto-install additional theme snaps to match the theme you have set.
But as you can see from my screenshots and comment I used three themes that aren’t part of that snap package. Yet somehow they are correctly picked up by snap-store.
i had a very similar looking issue after upgrading to 20.04 which was totally unrelared to snaps.
Xorg on intel does now use the modesetting xorg server, if you still have the formerly used xserver-xorg-video-intel installed on these systems you might get screen corruption, font issues and theme issues …