This sounds a bit weird, but I tried connecting to a FTP server with the exact same credentials on my iPad, iPhone X, and iPhone XS. Only the iPhone XS doesn’t work, shown in the attachments.
Append:
The error page shows up instantly. I also don’t see any activity in the FTP server log when it happens. I’ve also tried reinstalling the app and turning off iCloud sync. Not working.
Append 2:
Tried the Raeddle’s Documents app. It cannot connect to the FTP server as well. However both Infuse and Documents can connect to the SMB server on the same machine.
Append 3:
Turns out it was a fail2ban setting in the NAS that banned the access from the iPhone XS… This is awkward.
