I’ve found a workaround to the graphics glitches: Add a single symbol to a schematic, click Edit → Color Preferences. In the dialog you can select colors for the CAD symbols, when hovering slightly to the bottom right of a symbol, a white box should appear around a lot of black. Click that to select the text field and pick another color. Now all text should be visible again.
I haven’t tried it out much more than that, but at least it makes text visible again. It seems that the wine bug is only related to how the background is being drawn in Direct2D, so maybe there’s an easy fix on either the wine or QSPICE drawing code for it.
edit: i also opened an upstream bug here: WineHQ Bugzilla – Bug 55353 – D2D Rendering glitches in QSpice