Checked the logs of supervisor & core using journalctl (with help of How to get to your log after restart/restore & Debugging the Home Assistant Operating System | Home Assistant Developer Docs).
Following are the last few log messages from Supervisor & Core + all log messages preceeding the hickup.
Supervisor
Seems to be irrelevant, since the system still ran 1 min later (see “preceeding”)
Jul 21 09:36:54 homeassistant hassio_supervisor[569]: 23-07-21 11:36:54 INFO (MainThread) [supervisor.homeassistant.api] Updated Home Assistant API token
Jul 21 09:39:26 homeassistant hassio_supervisor[569]:
Jul 21 09:39:34 homeassistant hassio_supervisor[569]: 23-07-21 11:39:34 INFO (MainThread) [supervisor.homeassistant.secrets] Request secret backup_password
Jul 21 09:39:47 homeassistant hassio_supervisor[569]: 23-07-21 11:39:47 INFO (MainThread) [supervisor.updater] Fetching update data from https://version.home-assistant.io/stable.json
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.check] Starting system checks with state CoreState.RUNNING
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.checks.base] Run check for IssueType.MULTIPLE_DATA_DISKS/ContextType.SYSTEM
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.checks.base] Run check for IssueType.PWNED/ContextType.ADDON
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.checks.base] Run check for IssueType.NO_CURRENT_BACKUP/ContextType.SYSTEM
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.checks.base] Run check for IssueType.DNS_SERVER_IPV6_ERROR/ContextType.DNS_SERVER
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.checks.base] Run check for IssueType.DNS_SERVER_FAILED/ContextType.DNS_SERVER
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.checks.base] Run check for IssueType.IPV4_CONNECTION_PROBLEM/ContextType.SYSTEM
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.checks.base] Run check for IssueType.FREE_SPACE/ContextType.SYSTEM
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.checks.base] Run check for IssueType.DOCKER_CONFIG/ContextType.SYSTEM
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.checks.base] Run check for IssueType.TRUST/ContextType.SUPERVISOR
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.checks.base] Run check for IssueType.SECURITY/ContextType.CORE
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.check] System checks complete
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.evaluate] Starting system evaluation with state CoreState.RUNNING
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.evaluate] System evaluation complete
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.fixup] Starting system autofix at state CoreState.RUNNING
Jul 21 09:42:42 homeassistant hassio_supervisor[569]: 23-07-21 11:42:42 INFO (MainThread) [supervisor.resolution.fixup] System autofix complete
Jul 21 09:44:26 homeassistant hassio_supervisor[569]:
Jul 21 09:44:43 homeassistant hassio_supervisor[569]: 23-07-21 11:44:43 INFO (MainThread) [supervisor.homeassistant.secrets] Request secret backup_password
-- Boot 6fc9a46b0f764aa78a1ee9315dcb89a4 --
Jul 29 18:24:25 homeassistant hassio_supervisor[553]: s6-rc: info: service s6rc-oneshot-runner: starting
Core
Seems to be completely unrelated
Jul 21 09:36:41 homeassistant homeassistant[569]: 2023-07-21 11:36:41.986 ERROR (MainThread) [homeassistant.components.automation.getter_heizungsmodus] Heizung: Modus get: Error executing script. Error for call_service at pos 1: Invalid option: unknown (possible options: aus, nur WW, Heizen u
Jul 21 09:36:41 homeassistant homeassistant[569]: 2023-07-21 11:36:41.995 ERROR (MainThread) [homeassistant.components.automation.getter_heizungsmodus] Error while executing automation automation.getter_heizungsmodus: Invalid option: unknown (possible options: aus, nur WW, Heizen und WW)
Jul 21 09:37:42 homeassistant homeassistant[569]: 2023-07-21 11:37:42.879 ERROR (MainThread) [homeassistant.components.automation.getter_heizungsmodus] Heizung: Modus get: Error executing script. Error for call_service at pos 1: Invalid option: unknown (possible options: aus, nur WW, Heizen u
Jul 21 09:37:42 homeassistant homeassistant[569]: 2023-07-21 11:37:42.888 ERROR (MainThread) [homeassistant.components.automation.getter_heizungsmodus] Error while executing automation automation.getter_heizungsmodus: Invalid option: unknown (possible options: aus, nur WW, Heizen und WW)
-- Boot 6fc9a46b0f764aa78a1ee9315dcb89a4 --
Jul 29 18:25:51 homeassistant homeassistant[553]: s6-rc: info: service s6rc-oneshot-runner: starting
Preceeding
Jul 21 09:45:29 homeassistant addon_core_configurator[569]: INFO:2023-07-21 11:45:29,281:hass_configurator.configurator:127.0.0.1 - "GET / HTTP/1.1" 200 -
Jul 21 09:45:31 homeassistant hassio_dns[569]: [INFO] 127.0.0.1:48945 - 8213 "PTR IN XXX.XXX.XXX.XXX.in-addr.arpa. udp 56 true 2048" NXDOMAIN qr,rd,ra 45 0.025264369s
Jul 21 09:45:31 homeassistant hassio_dns[569]: [INFO] 172.30.32.1:54066 - 8213 "PTR IN XXX.XXX.XXX.XXX.in-addr.arpa. udp 45 false 512" NXDOMAIN qr,rd,ra 45 0.040048083s
Jul 21 09:45:31 homeassistant hassio_dns[569]: [INFO] 127.0.0.1:48945 - 21260 "PTR IN XXX.XXX.XXX.XXX.in-addr.arpa. udp 55 true 2048" NXDOMAIN qr,rd,ra 44 0.024549987s
Jul 21 09:45:31 homeassistant hassio_dns[569]: [INFO] 172.30.32.1:39321 - 21260 "PTR IN XXX.XXX.XXX.XXX.in-addr.arpa. udp 44 false 512" NXDOMAIN qr,rd,ra 44 0.038033026s
Jul 21 09:45:31 homeassistant hassio_dns[569]: [INFO] 127.0.0.1:48945 - 49743 "PTR IN XXX.XXX.XXX.XXX.in-addr.arpa. udp 55 true 2048" NXDOMAIN qr,rd,ra 44 0.007673401s
-- Boot 6fc9a46b0f764aa78a1ee9315dcb89a4 --
Apr 04 10:55:35 homeassistant systemd-timesyncd[544]: System clock time unset or jumped backwards, restoring from recorded timestamp: Sat 2023-07-29 18:21:40 UTC