STM32G0

The STM32G0 line are low-cost high-efficiency parts with M0+ cores.

They're cheaper, or comparable to, various speciality I2C parts we were looking to use, and have reduced requirements for external parts. For instance, we can just program I2C addresses into them, instead of needing to be able to configure them. They've also got integrated oscillators, and we can load them with intelligent signal processing & interrupt-triggering routines, to reduce load on the main board.

Subtleties

None yet! Hopefully it stays that way.

Noteworthy ST docs, and commentary

Getting started with STM32G0 Series hardware development

Basic hardware requirements, with reference schematic. The 'G0 requirements are significantly reduced compared to the STM32H7.