I was able to save a URL from my iPhone to the To Import directory. When I got back to my Mac, the file had been turned into a webarchive in EF, which is all good and I can view it.
However, if I try to open the webarchive file through the file system (on this machine, on another Mac, on my iPad using Documents), I’m unable to open it. On both Macs, I get the message “[name] cannot be opened because it is from an unidentified developer. macOS cannot verify that this app is free from malware.” I am running macOS 10.15.6, and on my iPad I am running iOS 13 (whatever the latest dot release).
I have a screen shot of the error, if that’s useful.
I’m not sure what causes it, but sometimes macOS marks documents as quarantined, and it seems to treat them as untrusted applications even though they are just documents. Opening using the contextual menu should work. Or perhaps one of the workarounds here will help.
It’s also possible to bulk-remove the quarantine from files using the xattr -c command in Terminal or Sandstrip.
It doesn’t throw an error - the webarchive file opens into Documents, and just shows a blank page. This happens even if the quarantine has been “lifted”. I did email Readdle to see if they had any ideas, but have not heard back.