update unsupported mac with OS X lion to APFS 10.15
There is software on the logic board which is referred to as firmware. This is the software that first executes when a Mac starts up. The firmware is capable of reading partitions using various formats such as JHFS+. When Apple introduced the APFS format, Apple only provided firmware updates for certain Mac models. Older Macs can not boot from APFS formatted partitions, because the firmware does not recognize the APFS format. Your Mac is one such model. There is no way to fix this. The macOS 10.15 operating system can only boot from APFS formatted partitions.