Aminet

The original 'App Store' from the days when a phone was a phone and just let you talk to people.

Here you can generally download software for Classic Amiga only, however from time to time you can find AmigaOS 4.x software uploaded to here.

Look for the boing ball logo for AmigaOS 4.x native applications and the checkmark for Classic software; many of which will still run on AmigaOS perfectly fine.