End2Encryption file headers/extension to exclude from backup

I’m looking to use a backup solution together that offers deduplication/incremental updates, while offering clients the option to use end 2 end encryption. Encryption has obvious issues with deduplication and/or incremental updates: a small change will create a completely new unique file.

As such I want to create two backup history profiles. Unencrypted files can be kept much longer than the encrypted data. But this does require being able to recognize a encrypted file. Do the E2EE files use a certain extension or file header?

I would check an encrypted file in the Nextcloud storage folder if it has a different extension or some header. I’m currently not using this option, since you have it enabled already you could do it yourself…

I am actually not pending the desktop client sync issue.