> PREEMPT_NONE: The kernel almost never interrupts a running thread

This seems confused. These are options for preemptibility of the kernel, which is a relatively modern fearure. Userspace could always be preempted and these options do not change anything there. The kernel must in any case frequently interrupt threads and processes to implement preemptive multitasking which Linux of course had since the beginning.

Read more eg at https://lwn.net/Articles/944686/ or help texts at https://github.com/torvalds/linux/blob/master/kernel/Kconfig...