Earlier, I already showed how to install macOS Mojave on an old Apple computer. Now I’ll do the same with macos 10.15 Catalina. Today this is a latest mac os.
Format your Flash Drive (16Gb or more) Mac OS Extended (Journaled) GUID Partition Map by Disk Utility.
Use Patcher to make macOS 10.15 bootable USB.
Bot from Catalina Install USB.
Do not forget run Post Install for your fresh macOS Catalina.