It looks like the error message is misleading - the messages do in fact arrive, but the notus files are not found:
$ docker compose -f docker-compose.yml -p greenbone-community-edition logs -f ospd-openvas
ospd-openvas-1 | OSPD[7] 2024-02-13 07:23:00,854: INFO: (ospd.main) Starting OSPd OpenVAS version 22.6.2.
ospd-openvas-1 | OSPD[7] 2024-02-13 07:23:00,859: INFO: (ospd_openvas.messaging.mqtt) Successfully connected to MQTT broker
ospd-openvas-1 | OSPD[7] 2024-02-13 07:23:10,910: INFO: (ospd_openvas.daemon) Loading VTs. Scans will be [requested|queued] until VTs are loaded. This may take a few minutes, please wait...
ospd-openvas-1 | OSPD[7] 2024-02-13 07:24:08,737: INFO: (ospd_openvas.daemon) Finished loading VTs. The VT cache has been updated from version 202402120557 to 202402130613.
ospd-openvas-1 | OSPD[7] 2024-02-13 07:28:25,067: INFO: (ospd.command.command) Scan f1b5d4ed-daf9-4e7c-bf65-22acf8aaf91c added to the queue in position 2.
ospd-openvas-1 | OSPD[7] 2024-02-13 07:28:29,992: INFO: (ospd.ospd) Currently 1 queued scans.
ospd-openvas-1 | OSPD[7] 2024-02-13 07:28:30,178: INFO: (ospd.ospd) Starting scan f1b5d4ed-daf9-4e7c-bf65-22acf8aaf91c.
ospd-openvas-1 | OSPD[7] 2024-02-13 07:47:37,712: WARNING: (ospd_openvas.daemon) Invalid VT oid for a result
ospd-openvas-1 | OSPD[7] 2024-02-13 07:48:39,410: WARNING: (ospd_openvas.daemon) Invalid VT oid for a result
ospd-openvas-1 | OSPD[7] 2024-02-13 07:48:40,412: INFO: (ospd.ospd) f1b5d4ed-daf9-4e7c-bf65-22acf8aaf91c: Host scan finished.
ospd-openvas-1 | OSPD[7] 2024-02-13 07:48:40,414: INFO: (ospd.ospd) f1b5d4ed-daf9-4e7c-bf65-22acf8aaf91c: Scan finished.
$ docker compose -f docker-compose.yml -p greenbone-community-edition logs -f notus-scanner
notus-scanner-1 | 2024-02-13 07:22:52,651 notus-scanner: INFO: (notus.scanner.daemon) Starting notus-scanner version 22.6.2.
notus-scanner-1 | 2024-02-13 07:46:37,484 notus-scanner: WARNING: (notus.scanner.loader.json) Could not load advisories from /var/lib/notus/products/almalinux_9.notus. File does not exist.
notus-scanner-1 | 2024-02-13 07:46:37,484 notus-scanner: ERROR: (notus.scanner.scanner) Unable to start scan for 10.138.0.14: No advisories for OS-release AlmaLinux 9 found. Check if the OS-release is correct and the corresponding advisories are given.
notus-scanner-1 | 2024-02-13 07:47:38,360 notus-scanner: WARNING: (notus.scanner.loader.json) Could not load advisories from /var/lib/notus/products/almalinux_9.notus. File does not exist.
notus-scanner-1 | 2024-02-13 07:47:38,360 notus-scanner: ERROR: (notus.scanner.scanner) Unable to start scan for 10.138.0.21: No advisories for OS-release AlmaLinux 9 found. Check if the OS-release is correct and the corresponding advisories are given.
In a related topic, there is a link to the docs where AlmaLinux is listed between the available LSC VT families, but in the ospd-openvas container in /var/lib/notus/products there are only files for Debian, EulerOS, Slackware, Suse, Ubuntu. Same in the Community Feed Rsync. So is AlmaLinux an enterprise grade product with regard to the feed comparison?