Whilst PCW's recipe above got me onto the PREEMPT_RT kernel about 5 years ago, there is little reason to do it today as there are patches available which can apply the kernel without compilation.
Tommy does a good job documenting the process for Mint 19.3 here
forum.linuxcnc.org/9-installing-linuxcnc...nd-easy-installation
It works and can be done in minutes not hours.
But being able to compile the kernel is pretty cool
I've been compiling linux kernel's since the early to mid 90's. I even have my moment of fame mentioned in the kernel source. I was just looking at the differances between rtai from rtai.org and rt patches from linux.org. linuxcnc has both mentioned in the configure, so I was trying it out. I misspoke about the system running my plasma. it's actually and I3, but has terrible latency issues..
