Errors after switching to community feed on GSM-appliance

Hi there,

we have a GSM600 appliance but unfortunately (currently) no enterprise-subscription.

After syncing from the community-feed, sync log shows no errors, but scans refuse to start with the following error:

Interrupting scan because GVM is exiting.
VTs list is empty

Journal keeps repeating:

Erroneous or missing signature for checksums file /opt/greenbone/feed/plugins/sha256sums
No checksum for /opt/greenbone/feed/plugins/
OSPD[803] ERROR: (ospd_openvas.openvas) OpenVAS Scanner failed to load VTs. Command ‘[‘openvas’, ‘–update-vt-info’]’ returned non-zero exit status 1.

I found a post here explaining that the community feed integrity key is missing:

But I’m not sure how to solve this on Greenbone OS as the mentioned post says it should be included already. Should I enable superuser-access and load the key for a specific user, and if this is the case, what is the correct user?

[edit] I enabled superuser access and worked around the signature check by setting nasl_no_signature_check to yes, so scans are running again but it would be nice to get the signature verificiation working again.

Another problem is that I am not able to update due to complaints about system integrity (which already were shown before). It seems the apt-key has expired in february (The sytem was not able to update for a while due to firewall restrictions). Where can I find a recent key? Is is possible to switch trial version at all without a subscription? [/edit]

Thanks for any help