First, I agree that find_package with a version if fine, because the default KPMCore.ConfigVersion.cmake file just accept the version if the installed version is greather than the requested version.
For me there is one bug: When settings the flags for the boot partition, it does not select type EF00 although KPMCore version is greather than 4.0 (it is 4.1).
You say it does not belongs because bootldr module set EF00... Well, it does not seems to do it for me.
But also this is a problem because the directory path to conf_path seems to be created prior to bootldir module loaded. And also the creation of the EFI BootXXXX variable that will allows to access the newly installed OS seems to be done prior to the bootldr module, and only if the /boot partition have type EF00... so it is important that it be set by kpmcore near the beginning.
Using install alongside a partition... or by replacing a partiton (likely the free space which is not really a partition but seems to act like it for calamares) would not help to discover the bug because it make you choose a UEFI partition (with coreect EF00 type)... so that it does not change the type of the partition... so it does not do the bug. A full disk install would logically have to set the type of a newly partition, but I don't feel like erasing my hard drive. (I could install an other however).