My OS course covers operating systems from a system call perspective (POSIX, processes, synchronization and the usual things), but doesn't include kernel/device driver development, so we only had to cope with small differences in syscall behavior here.
Supporting Linux/WSL and macOS was a bit more problematic for the compiler backend exercise due to subtle differences in the supported assembler syntax and linker behavior between Linux and macOS as well as some students who might already own an M1 Mac.
Luckily, Rosetta happily executes the x86 binaries my students created using the macOS x86 crossassembler and -linker, so that turned out to be not a problem (I was hoping that a student would build an Aarch64 backend, but that didn't happen). None of my students seems to own a Pinebook or MNT Reform, so Linux/Arm was not a problem this year.
Now, in CS we're one of the edge cases where booting VMs and parallel systems is part of the deal. In the Chromebook configuration it's actually 3 systems running at the same time so more RAM has a direct impact on performance.
(point taken on the Thinkpad price, I also think if we settle on a refurbished Chromebook, we could so the same for the Thinkpad and perhaps get it a bit lower)