Curiously, in what no academic could have predicted, millions of people interact with a microkernel every day, and it was written by freaking Nintendo of all possible companies. (The Switch is a custom microkernel called Horizon; not FreeBSD, not Linux, not Android.) Almost every other consumer device is monolithic or hybrid.

While the Switch was broken early, this was due to NVIDIA's buggy boot code. The operating system itself... you could literally pwn WebKit or the Bluetooth driver, and get absolutely nowhere. SciresM famously reimplemented the kernel in an open source fashion (Mesosphere) and the secure monitor code (Exosphere), and has publicly stated they have zero possible security bugs in his eyes. That was in 2020 and there have not been any reports of kernel security bugs since.

To be fair, microkernels are also highly successful in embedded devices and auxiliary processors. It’s just that you don’t usually directly interact with them. For example, Intel ME runs MINIX, and Apple’s Secure Enclave Processor runs L4. Also most OSes these days have some kind of hypervisor/secure monitor that’s more privileged than the regular kernel: TEE on Android, SPTM on Apple, VBS on Windows, and proprietary ones on all the game consoles. They vary in how much functionality they’re actually responsible for, but if it’s a significant amount then they tend to have a microkernel-ish design internally.

Another example of microkernel-based systems you do interact with is car infotainment systems, where QNX has apparently seen a lot of use – though I think these days it’s being displaced by Linux and Android Automotive? I don’t actually know much about that industry.