RP2350 adds secure boot and encrypted boot. I am working on a little hardware device for a CTF and selected it as my MCU so participants can't just dump the flash to grab the flags.

> read the RP2350 errata carefully

Even the latest rev? Can you elaborate a bit?

Mixed signal means analog and digital

> Almost any embedded application needs mixed signal interfaces.

For the vast majority of embedded applications you can simply pick an MCU that has the hardware peripherals they need. That's why XMOS was never very successful. (They thought of this idea long ago.) Not saying it isn't cool.