fso-frameworkd is installed but I had indeed no config. I saved the file in /etc (and in /etc//om-gta02 as the link suggests) and rebooted the VM. But according to strace neither the deamon nor the UI applications try to read the config file. It seems like phoneuid needs quite a while until it accepts connections from the UI applications. If I start one within 30 seconds after starting the deamon I still get the timeout. If I wait two minutes phoneui-quick-settings comes up and I can switch the autodimming slider. However, after another two minutes this window is unresponsive and I get timeouts again when starting new UI applications (for example from the dialer). I don't see a pattern.