Where taillights are on the trunk lid I always suspect the wiring harness first as it's usually the wires chafing or bending repeatedly causing the short. If you have other issues like the plate light or the automatic lid opener isn't working then it's almost certainly the harness.

However, testing fuses and relays is easy and quick, and using a multimeter you can check for power all along the way. Digging into the harness can be time consuming - often you have to pull some trim to get at it - so it makes good sense to check the easy things first to eliminate them as possibilities.

In my experience the usual suspects are:

1. Broken bulb, but the filament looks intact.
2. Broken wire harness on the hinge of the trunk lid.

Should there be a blown fuse, it won't help just replacing the fuses, the root cause is still there.

There are cars out there that detect a broken light and shut down the power to the light. Those are more difficult to test, as a defective bulb gets mis-diagnosed as a broken harness, or something else that causes no power to the wire.

The root-cause of the issue is sought in a subsequent link.

Fuse 28 is the culprit. As Martin indicated, the root cause is unknown. Replacing the fuse seems to have (at least temporarily) solved the problem.

Wondering if the root cause has something to do with the unusual high blinking rate of the left turn signal.

Location of fuse:

After fuse replacement: