Linux on RISC-V is real, china is using & standardizing on it. Ditch arm, skip RPI, ignore STM-32, and scoff at TI, .. RISC-V is the future.
While you're at it - skip micropython, skip the OS Linux - use RUST and target RISC-V directly.
The cost of RISC-V is cheap and will only continue to plummet, nothing in the IOT space is going to compete with RISC-V except absurdly expensive niche proprietary solutions that were engineered before the blackhole-esque super-nova gravity hole that is RISC-V which is happening right now in the IOT space. I'm not even sure those will survive, ..
The RISC-V options are only going to continue to increase. I say this because China is using RISC-V for most of it's future everything, it's basically the national chip and there are literally tens of thousands of developers & engineers coming out of school into this ecosystem every single day.
Do not use micropython, avoid all these runtime debugging headaches. Yeah, it might take you a few months or even years to learn RUST, but the concurrency, the power saving, the deterministic behaviors - oh joy! The headaches you will save, the extra rest at night and reduced stress will increase your lifespan.
Qemu RISC-V for emulation + testing and you'll save yourself a ton of time only deploying and supporting code that works. Full simulated environments, you can test in parallel in the cloud, few platforms can do that! RISC-V + RUST it's a joy.
Fewer crashes in the field-- and let me tell ya! .. when you're doing anything IOT that is the only thing that matters - never having a crash in the field, that's better than chocolate cake.