Great answer, Id be really into running an OS made with a microkernel with majority of code in a memory-safe language - sadly seems like it would be a long way away.

Windows has also expressed interest to move to a language like Rust throughout the OS, instead of a microkernel they use a virtualization security approach by having Windows components run in their own virtualized environments. (https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/oem-vbs)

There is another project (Xous) that does the same thing you described but is mobile and has a hardware device to boot. Really cool but still experimentative: https://www.crowdsupply.com/sutajio-kosagi/precursor

Sadly it has no cellular network so it isn't really a phone, and I believe it may be lacking in the hardware security department since it has no security modules to be as open-source as possible. Worried it could be exploited like a Trezor would...

GrapheneOS also expressed interest to move to a microkernel which runs Android on top via virtualization. https://twitter.com/GrapheneOS/status/1586793216413769729