Kernelcare not available anymore?

Hi,

this is not something we (can) control in any way.
Have you tried asking the company/team behind Kernelcare directly about it?
 
CloudLinux who develop KernelCare and other products are very targeted in where they spend their development resources.

It is not the first time they have added support for software on their products only to quietly let all development efforts languish.

Raise a ticket with them and ask what the current status is, but have a plan if the answer is that they are not prioritising Proxmox.