The only officially recommended file encryption app for iOS is Cryptomator which locks essential functionality behind a paywall. PicoCrypt used to be recommended and is available on the web but it has a file size limit of 512 MiB which is too small for me. It also means fully trusting the JavaScript won’t ever include a backdoor which I don’t like.
The only free open source option I could find is Paranoia File Encryption Lite which might not have the savviest developers? I’m looking for alternatives that seem reliable and ideally are audited and open source if possible.