Preempt_RT is a set of patches for the Linux kernel. It modifies the kernel so that it becomes (almost) completely preemptive. The classic kernel spinlocks are replaced by mutexes which support priority inheritance. In addition, the handling of all interrupts is outsourced to separate kernel threads.
From 2024 on Preemp-RT was fully merged and enabled in mainline Linux for popular architectures.
Choose a machine. See Tested devices for reference
Install a Linux distribution. You can use UNetbootin to create an bootable Live USB drive.
To test the best possible RT performance Build a Preempt-RT Kernel with minimal configuration
If you are not satisfied with the performance of your system, tune your system.