I have a Trident TVGA 8900 attached to my OSSC. I two kinds of vertical artifacts. One is due to smapling, and I can get rid of it by allowing for 2x upsampling in the settings. Sew the LOOM screenshots for a comparison.

The other is more prominent in solid colored screens in text mode. I wonder if this is due to the VGA card, cable, or whatever and if I can fix it.

See e.g. this Dr Hardware screenshot: