Sorry.
In itself, of course, correct.
I assumed that you might have to approach the setting differently for Linux in general.
I have had the same case with a Windows VM, there it worked without problems.
ErrorWarningSystemArrayLogin
-smp 8,sockets=1,dies=1,cores=4,threads=2 \
-uuid 165679af-6cdc-3eac-0deb-4b607e9a216e \
-no-user-config \
-nodefaults \
-chardev socket,id=charmonitor,fd=34,server,nowait \
-mon chardev=charmonitor,id=monitor,mode=control \
-rtc base=utc,driftfix=slew \
-global kvm-pit.lost_tick_policy=delay \
-no-hpet \
-no-shutdown \
-boot strict=on \
-device pcie-root-port,port=0x10,chassis=1,id=pci.1,bus=pcie.0,multifunction=on,addr=0x2 \
-device pcie-root-port,port=0x11,chassis=2,id=pci.2,bus=pcie.0,addr=0x2.0x1 \
-device pcie-root-port,port=0x12,chassis=3,id=pci.3,bus=pcie.0,addr=0x2.0x2 \
-device pcie-root-port,port=0x13,chassis=4,id=pci.4,bus=pcie.0,addr=0x2.0x3 \
-device pcie-root-port,port=0x14,chassis=5,id=pci.5,bus=pcie.0,addr=0x2.0x4 \
-device ich9-usb-ehci1,id=usb,bus=pcie.0,addr=0x7.0x7 \
-device ich9-usb-uhci1,masterbus=usb.0,firstport=0,bus=pcie.0,multifunction=on,addr=0x7 \
-device ich9-usb-uhci2,masterbus=usb.0,firstport=2,bus=pcie.0,addr=0x7.0x1 \
-device ich9-usb-uhci3,masterbus=usb.0,firstport=4,bus=pcie.0,addr=0x7.0x2 \
-device virtio-serial-pci,id=virtio-serial0,bus=pci.2,addr=0x0 \
-blockdev '{"driver":"file","filename":"/mnt/cache/domains/ExtDocker/vdisk1.img","node-name":"libvirt-1-storage","cache":{"direct":false,"no-flush":false},"auto-read-only":true,"discard":"unmap"}' \
-blockdev '{"node-name":"libvirt-1-format","read-only":false,"cache":{"direct":false,"no-flush":false},"driver":"raw","file":"libvirt-1-storage"}' \
-device virtio-blk-pci,bus=pci.3,addr=0x0,drive=libvirt-1-format,id=virtio-disk2,bootindex=1,write-cache=on \
-netdev tap,fd=36,id=hostnet0 \
-device virtio-net,netdev=hostnet0,id=net0,mac=52:54:00:01:3d:3e,bus=pci.1,addr=0x0 \
-chardev pty,id=charserial0 \
-device isa-serial,chardev=charserial0,id=serial0 \
-chardev socket,id=charchannel0,fd=37,server,nowait \
-device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0 \
-device usb-tablet,id=input0,bus=usb.0,port=1 \
-vnc 0.0.0.0:1,websocket=5701 \
-k de \
-device qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,vram64_size_mb=0,vgamem_mb=16,max_outputs=1,bus=pcie.0,addr=0x1 \
-device virtio-balloon-pci,id=balloon0,bus=pci.4,addr=0x0 \
-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
-msg timestamp=on
2022-01-02 16:45:49.876+0000: Domain id=30 is tainted: high-privileges
2022-01-02 16:45:49.876+0000: Domain id=30 is tainted: host-cpu
char device redirected to /dev/pts/4 (label charserial0)