340.102 4.x kernels RT-Preempt patch

We have some boxes which are running 4.x series kernels but need the legacy 340.102 driver.

We want to update with a unit that requires RT (preempt) .

I’ve seen there are various patch options for supporting preempt scheduling, bit nothing for newer kernels and legacy hardware. Do such patches exist?

On a more general note, is this a reliable option? The CPU’s are add in boards so would we be better off just ditching them? Which boards can support RT without the patch?