I know of a couple of rather fancy, proprietary 2-way radio trunking systems products that use local MS SQL on the back end, to keep track of configs for individual subscriber radios and system configurations for the radio repeaters.

(What's that? Well, if you ever walk into a place like a gigantic oil refinery, you'll see a bunch of people working there. If you look long enough, you'll notice that each of them have an expensive-looking radio ("walkie talkie") on their hip. Some of those radios may be my fault -- and of those that are, there's an MS SQL database that knows exactly how it was programmed. But I didn't pick it; that's just how the system operates.)

Yep. Cabinet Vision as of 3 years ago required installing both SQL Server 2016 and 2019, plus 2010-vintage Microsoft Jet database, plus Powershell 2.0, plus .NET 3.5.

It’s completely dominant in its industry and has no real competition. Pricing starts at $200 a month for the most basic, single user setup and goes up (way up) from there.

And no, it doesn’t work on ARM, at all. I tried.

Which can also run on Linux now.