Update: neither cause nor patch were correct the option man snapclient suggests for changing niceness, is --daemon=<nice value>, and that's what I'm doing in my conf file, but the systemd service in its current form is of type simple, and expects the main process to run, not fork and daemonize
that's fixable with [Service] Type=forking Nice=-20 EnvironmentFile=-/etc/default/snapclient ExecStart=/usr/bin/snapclient --logsink=system --daemon=-3 $SNAPCLIENT_OPTS [..] like this, systemd will always run snapclient as a daemon. passing the --daemon option in the conf file, becomes safe. Nice=-20 will be overridden by --daemon=-3 (the default as per manpage, but although desirable, doesn't happen), and latter --daemon=<nice value> options sourced from the conf file, will be allowed all values apparantly, systemd does the variable substitution after all arguably, setting niceness is a core functionality for ensuring an audio streaming service's smooth and glitch-less operation, which could raise the bug severity
