@Belgarath "Employer-sponsored health coverage" refers to any group health plan in this context. So that includes dental and vision elections. The IRS has informally confirmed this.
Note that the relaxed election change rules don't actually come from the CARES Act. They come from IRS Notice 2020-29: https://www.irs.gov/pub/irs-drop/n-20-29.pdf
Also note that any mid-year enrollment or plan option change outside of a standard §125 permitted election change event would have to be approved by the carrier (or stop-loss provider if self-insured). Easier said than done.