What file systems can I use for a 128GB sdcard on Android 7.1, used as portable storage
If 'journaling' is a requirement, then the EXT family (preferrably ext4) mighy be your only choice. Otherwise exFAT is the best. Just FYI, data safety depends more on your hardware rather than software (assume there's no malware), including filesystems. Any FS on a bad drive fails, and any FS on a good drive makes few differences.

It is definitely sure that if you format it to ext4, you'll have to frequently chmod -R 777 and chown -R 0.1028 (which is actually root:sdcard_r) to ensure apps work fine. Different apps have different UIDs &amp; GIDs and upon creating a file, the owner groups are set as the app's U&amp;G, while permissions are set according to the effective thread's umask.
Another notice is that Linux ACL is not supported by Android, whereas SELinux is, which can cause.
The FAT family is better for not having permission support, thus preventing "permission chaos" from happening. exFAT is my personal preference for shared storages. There's no regular maintenance required.
Since you're asking here, an Android community, I'm not going to discuss NTFS &amp; Apple's HFS as they can hardly be recognized by a common Android device. Of course you can add the support for those by yourself, but it's mainly a concern of developers.