Replacing Ubuntu kernel on Pi 4B

I used to enable Ubuntu realtime kernel or lowlatency kernel in my other x64 machines (i.e. pro enable realtime-kernel). Yet I can’t do it on Pi. Now I got 3 kernels inside Pi, viz, ordinary one, RT, and lowlatency, but only the ordinary kernel is boot.

As I can’t find the answer in Google, may I know how to do it on Pi 4B? Or was Ubuntu simply not supporting RT kernel in Pi?

Thanks all. :slightly_smiling_face: