Install macOS Catalina on old Apple hardware

The best way to do this is to follow the procedure the "dosdude1" has created.

Go to his website dosdude1.com.

For Catalina specific: http://dosdude1.com/catalina/

If you need a USB install for Windows 10, then do this from a PC/Laptop with Windows 10 running.

Go to the Microsoft site and create USB install media from there with the Microsoft "MediaCreationTool". This will result in a USB stick formatted with FAT32 and the installer files smaller then 4 GB!!!

Note: It is possible to do from macOS, but then you need a file splitter program for the large 4GB+ files in the ISO (You need to have a FAT32 AND not a exFAT to get it booting)..