Thanks @augsch
Finally, I was able to start sys-audio after your findings.
Unfortunately, I cannot start win qubes. Now it gives me error:
Dec 27 15:17:57 dom0 libvirtd[1808]: internal error: libxenlight failed to create new domain ‘win10’
Dec 27 15:17:57 dom0 qubesd[72401]: vm.win10: Start failed: internal error: libxenlight failed to create new domain ‘win10’
When I manually set domid (sys-audio’s xid) in stubdoms, no problem with any of these. So, this guide isn’t accurate for all.