Comment 12 for bug 1869796

The two most similar working/failing sockets have no diff that IMHO would explain the behavior:
root@f2:~# diff -Naur /lib/systemd/system/libvirtd.socket /lib/systemd/system/libvirtd-ro.socket
--- /lib/systemd/system/libvirtd.socket 2020-03-20 09:34:19.000000000 +0000
+++ /lib/systemd/system/libvirtd-ro.socket 2020-03-20 09:34:19.000000000 +0000
@@ -1,12 +1,14 @@
 [Unit]
-Description=Libvirt local socket
+Description=Libvirt local read-only socket
 Before=libvirtd.service
+BindsTo=libvirtd.socket
+After=libvirtd.socket

 [Socket]
 # The directory must match the /etc/libvirt/libvirtd.conf unix_sock_dir setting
 # when using systemd version < 227
-ListenStream=/run/libvirt/libvirt-sock
+ListenStream=/run/libvirt/libvirt-sock-ro
 Service=libvirtd.service
 SocketMode=0666