I'm a bit confused about the left rear turn signal issue. In 2022, only the RS and Premier Equinoxes had LED rear lights. The LT does not have LED.
That said, I recently saw a Youtube video of a white Equinox that had some body work done on the left rear, and the body shop did a poor job connecting the new light socket to the wiring harness. It was displaying the exact message you report. Mechanic replaced the offending wires and resolved the issue. The dealer had quoted some ridiculous price to replace the wiring harness. The mechanic fixed it for a small fraction of that. Ironically, it was also a white LT.