https://onelaboratories.us/rtai_lcnc/
Old RTAI Set:
sudo apt purge linuxcnc*
sudo apt purge flexgui*
sudo apt purge linux-headers-5.4.258-rtai*
sudo apt purge linux-image-5.4.258-rtai*
sudo apt purge rtai-modules-5.4.258*

https://onelaboratories.us/abc/
New RTAI Set:
sudo apt purge linuxcnc*
sudo apt purge linux-headers-5.4.279-rtai*
sudo apt purge linux-image-5.4.279-rtai*
sudo apt purge rtai-modules-5.4.279*

sudo dpkg -i linuxcnc_2.9.2_amd64.deb
sudo dpkg -i linux-headers-5.4.279-rtai-amd64_5.4.279-rtai-amd64-1_amd64.deb
sudo dpkg -i linux-image-5.4.279-rtai-amd64_5.4.279-rtai-amd64-1_amd64.deb
sudo dpkg -i rtai-modules-5.4.279_5.3.3-linuxcnc-delta_amd64.deb

sudo /usr/realtime-5.4.258-rtai-amd64/testsuite/run
(Ctrl=C to cancel)
or
sudo /usr/realtime-5.4.279-rtai-amd64/testsuite/run
(Ctrl=C to cancel)