If you have access to a raw ext4 image and want to read it without mounting it you can use https://github.com/nlitsme/extfstools (This will work on low privilege (which can not mount things) linux enviroments as well). It does the job of reading images directly, that means it will read EXT4 filesystems, if you already have the raw data readable somewhere, it will not do the job of reading the raw data hard drive or SD card directly, it is a commandline utility. (This means it can read your_ext4.img but it won't read raw data directly from the hard drive, this can be useful to you if you have qcow2 images or virtual machine images you can read on your filesystem normally.) If you can somehow dump sd card contents into an image, and if you can dump an ext2/3/4 partition, this will work!

If you have access to a raw ext4 image and want to read it without mounting it you can use https://github.com/nlitsme/extfstools (This will work on low privilege (which can not mount things) linux enviroments as well). It does the job of reading images directly, that means it will read EXT4 filesystems, if you already have the raw data readable somewhere, it will not do the job of reading the raw data hard drive or SD card directly, it is a commandline utility. (This means it can read your_ext4.img but it won't read raw data directly from the hard drive, this can be useful to you if you have qcow2 images or virtual machine images you can read on your filesystem normally.) If you can somehow dump sd card contents into an image, and if you can dump an ext2/3/4 partition, this will work!

That being said, if you already have the image, you could just use 7zip.