I recently upgraded to MacOS Mojave using Dosdudes patcher and have been getting a few graphical anomalies in certain apps. I have included an example. It manifests as large black boxes over certain text or graphical windows/items and it doesn't seem to have much of a rhyme or rhythm to when or where it appears. Restarting apps and switching from light to dark mode or vice-versa does temporarily fix the issues sometimes. 
This is exactly why Apple made the cut-off for machines that don't support the Metal graphics framework.
You can expect all sorts of graphics glitches if you're trying to run an OS that expects hardware you don't have.
