In an other post I explained how to access and edit the data on an USB attached drive with the Linux "standard" ext4 filesystem.
In this post I will explain how to read, write or add files using Windows, File explorer, or Mac, Finder, without third party software !
You "just" need a Linux machine, but since you want to access an ext4 filesystem there probably are a machine in the surroundings ?
In this post I will use a "simple" Raspberry Pi(RPi) and the ext4 media attached to one of the USB ports.