In Gentoo, we rename crontab in sys-process/systemd-cron to crontab-systemd.
--- a/common/schedule.py
+++ b/common/schedule.py
@@ -33,7 +33,7 @@ def _determine_crontab_command() -> str:
     Raises:
         RuntimeError: If none of the supported commands available.
     """
-    to_check_commands = ['crontab', 'fcrontab']
+    to_check_commands = ['crontab', 'fcrontab', 'crontab-systemd']
     for cmd in to_check_commands:
         proc = subprocess.run(
             ['which', cmd],