Hm, weird. Are you using Secure Boot? The kernel in that repo won't work with Secure Boot because of the lack of the proper signing. If you must use Secure Boot, you may try the official Leap 15.2 kernel instead, found in http://download.opensuse.org/distribution/leap/15.2/repo/oss/ If it's not about Secure Boot, it must be another bug and worth to track down.