How to mount (or auto mount) a USB stick formatted with ext4 and be visible or working with apps on Android 5 Marshmallow and later versions?

The question appears in variant forms1 just to say it is ridiculous on Android that ext4 is the default file system that doesn't recognize USB pen drive formatted with ext4 (but Android 4.4 recognizes it without any problem). As a Linux user, this is a big regression, and I still have not found a way for a USB to be detected as a USB, like pens with FAT32 or NTFS. I have root on my device. --- 1 Related questions: - https://android.stackexchange.com/questions/176203/mounting-a-ext4-formatted-sdcard-on-android-marshmallow - https://android.stackexchange.com/questions/197959/partition-gets-unmounted-automatically-in-android-oreo - https://android.stackexchange.com/questions/123615/external-ext4-card-mounted-only-for-root-on-android-5-1-64-bits - https://android.stackexchange.com/questions/174308/how-to-use-an-ext4-formatted-sd-card-as-external-storage-with-working-app-permis