Bluetooth not working in MacBook Pro 2018 15 inch

Shortly after the warranty expired on this unit, Bluetooth functionality disappeared. We took it in to an authorized repair center for service, but were told the only fix was to replace the entire motherboard, to the tune about $900.

This was (and is) such a disappointment, because this was a very expensive unit. We regret not springing for AppleCare extended warranty ... but we also regret even buying this product in the first place. It's the first Apple product to ever make us feel that way. We had bought the most loaded model we could afford, and included 32GB of memory.

We've spent the subsequent years trying to get our money's worth from this beautiful but maddening machine, reminded of our poor choice any time we want to use a wireless mouse, Airdrop, or iPhone Hotspot.

(We've tried dongles as a solution, but they usually either don't work or don't last. I've spent a couple of days trying to get a Kinivo BTD400 to function. I can see in my System Report that it's connected, but I can't turn it on.)

The MacBook's internal Bluetooth malfunction seems like it might be a software or firmware issue. The Bluetooth worked fine until shortly after we updated the OS to Catalina. But when we took it in, both the repair center and Apple Support said that there was no software or firmware solution, just a motherboard replacement.

I'd be so happy to figure out a reasonable fix for this. Any Mandolorians out there who can show me The Way?

Here's what I see in my system report — Discoverable: Off.

Thanks for reading!