As a followup to the previous post, here's an update on the iOS 14 USB tethering problem on Linux. After some investigation, Matti Vuorela found that reducing the USB packet size by two bytes would actually fix the issue. A small patch was later commited to the Linux kernel and found its way to Linux and distributions stable releases. On Debian stable you'll need to upgrade to Buster 10.7 to get the fix.