I see your iOS 17 dev beta running on your primary iPhone and raise you Mac OS System 7 on a PocketChip. - The Verge

ThisDoesNotCompute has a fun video on running Mac OS System 7 on a PocketChip, a handheld computer from 2016 that was powered by a board similar to a Raspberry Pi. Bonus: the video includes a bit of history about the PocketChip and the board inside of it, including the downfall of the company that made it.