QNAP as Time Machine Backup
Issue: Mac is not able to use the QNAP as Time Machine backup. During backup it fails and says 'The network backup disk does not support the required capabilities'
Resolution: Disable kernel-mode SMB Daemon
Control Panel -> Win/Mac/NFS/WebDAV -> Advanced Options -> Untick 'Enable kernel-mode SMD daemon'
I had to restart the NAS for it to work.
Source: Time machine stopped working (solved with workaround) - QNAP NAS Community Forum