Latest secure kernels available in the repos for 32 (pae and non-pae) and 64 bit architecture.
5.8.7 (antiX-17, antiX-19, testing and sid)
4.19.143 (antiX-17, antiX-19, testing and sid)
4.9.235 (antiX-17, antiX-19, testing and sid)
4.4.235 (antiX-17, antiX-19, testing and sid)
Note: The 5.8.7 kernel might not build broadcom-sta wifi, nvidia drivers or virtualbox drivers (yet).