I regularly use both atmega328p (Arduino Uno) and stm32g0 (st-nucleo boards) microcontrollers for hobby projects. The linux toolchain for both are equally good. But the Nucleo boards are a lot cheaper than Arduino Uno/Mega boards, have a lot more capabilities, any are 32-bit microcontrollers.

I am actually fascinated with the things you can do with stm32 chips. If I ever do a commercial project, I would definitely use stm32 chips. Bare metal programming them has been a lot of fun.