MacOS can’t find boot loader or Macintosh HD

Yes, you were correct about not finding a drive. Disk Utility is not showing that a drive. I'm afraid my first thought was correct. Looks like the internal SSD has failed. Very unexpected for a 3 year old machine but electronic devices can fail. You will need to have this repaired.

Make an appointment at the Apple Genius Bar for service after the stores re-open. If you need to find an Apple Store - Find a Store - Apple. Also, see How to find your nearest Apple Authorized Service Provider (AASP) or Distributor (AAD). You may also get Apple authorized service at a local Best Buy or contact Apple Support for more options.

Contacting Apple Customer and Support Service

1. Apple Store Customer Service at 1-800-676-2775 or visit online Help for more information.
2. If you just purchased the product, then you get 90 days of free telephone support from the date of purchase of your Apple device.
3. Primary support help at Contact Support.
4. To contact product and tech support:  Contacting Apple for support and service including international calling numbers.

If you open Disk Utility and there is no selectable drive name of any kind listed in the sidebar, then the drive has failed. You will need to replace the drive. Your model uses an Apple SSD, so this is not a DIY repair. I'm curious as to how your were able to boot from the Recovery Volume and run First Aid, if there was no drive to select.

Perhaps you could post a clear and readable image of the Disk Utility window.

Erase and Install macOS from Scratch

If possible, back up your files.

1. Restart the computer. Immediately, at or before the chime, hold down the Command and R keys until the Apple logo and progress bar appear. Wait until the Utility Menu appears.
2. Select Disk Utility from the Utility Menu and click on the Continue button.
3. When Disk Utility loads select the target drive (out-dented entry w/type and size info) from the Device list.
4. Click on the Erase button in Disk Utility's toolbar. A panel will drop down.
5. Set the partition scheme to GUID.
6. Set the Format type to APFS (SSDs only) or Mac OS Extended (Journaled.)
7. Click on the Apply button, then wait for the Done button to activate and click on it.
8. Quit Disk Utility and return to the Utility Menu.
9. Select Install OS X and click on the Continue button.